Add a comment to note that pseudo-device bpf is required for DHCP.

This is mentioned in the Handbook but it is not as obvious to new
users why bpf is needed compared to the other largely self-explanatory
items in GENERIC.

PR:		conf/40855
MFC after:	1 week

sys/alpha/conf/GENERIC

@@ -190,6 +190,7 @@ device		faith		# IPv6-to-IPv4 relaying (translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter
 
 # USB support

sys/amd64/conf/GENERIC

@@ -239,6 +239,7 @@ device		faith		# IPv6-to-IPv4 relaying (translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter
 
 # USB support

sys/conf/NOTES

@@ -563,7 +563,7 @@ device		musycc	# LMC/SBE LMC1504 quad T1/E1
 #  The `bpf' device enables the Berkeley Packet Filter.  Be
 #  aware of the legal and administrative consequences of enabling this
 #  option.  The number of devices determines the maximum number of
-#  simultaneous BPF clients programs runnable.
+#  simultaneous BPF clients programs runnable.  DHCP requires bpf.
 #  The `disc' device implements a minimal network interface,
 #  which throws away all packets sent and never receives any.  It is
 #  included for testing purposes.  This shows up as the `ds' interface.

sys/i386/conf/GENERIC

@@ -261,6 +261,7 @@ device		faith		# IPv6-to-IPv4 relaying (translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter
 
 # USB support

sys/ia64/conf/GENERIC

@@ -148,4 +148,5 @@ device		uart		# Serial port (UART)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter

sys/pc98/conf/GENERIC

@@ -227,6 +227,7 @@ device		faith		# IPv6-to-IPv4 relaying (translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter
 
 # USB support

sys/powerpc/conf/GENERIC

@@ -116,6 +116,7 @@ device		faith		# IPv6-to-IPv4 relaying/(translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		#Berkeley packet filter
 
 # USB support

sys/sparc64/conf/GENERIC

@@ -192,6 +192,7 @@ device		faith		# IPv6-to-IPv4 relaying (translation)
 
 # The `bpf' device enables the Berkeley Packet Filter.
 # Be aware of the administrative consequences of enabling this!
+# Note that 'bpf' is required for DHCP.
 device		bpf		# Berkeley packet filter
 
 # USB support