Fix powerpc LINT build

tcpratelimit isn't supported as there's now atomic_add_64, so add it to the exclusion list
Add comment for why PPC_PROBE_CHIPSET is on the list
Remove UKBD_DFLT_KEYMAP now that ukbd works on all platforms.

sys/conf/makeLINT.mk

@@ -64,4 +64,5 @@ LINT: ${NOTES} ${MAKELINT_SED}
 	echo "nodevice mlx5" >> ${.TARGET}
 	echo "nodevice mlx5en" >> ${.TARGET}
 	echo "nodevice mlx5ib" >> ${.TARGET}
+	echo "nooptions	RATELIMIT" >> ${.TARGET}
 .endif

sys/powerpc/conf/NOTES

@@ -90,5 +90,4 @@ nodevice	dcons_crom
 # Options we don't want to deal with
 
 nooption	PPC_DEBUG
-nooption	PPC_PROBE_CHIPSET
-nooption 	UKBD_DFLT_KEYMAP
+nooption	PPC_PROBE_CHIPSET	# uses inb/outb