Update the comments concerning net_parse_rootpath to reflect what it is now

really doing

Reported by:	rgrimes
Reviewed by:	rgrimes
Differential Revision:	https://reviews.freebsd.org/D10959

sys/boot/common/dev_net.c

@@ -367,8 +367,20 @@ net_print(int verbose)
 }
 
 /*
- * Strip the server's address off of the rootpath if present and return it in
- * network byte order, leaving just the pathname part in the global rootpath.
+ * Parses the rootpath if present
+ *
+ * The rootpath format can be in the form
+ * <scheme>://ip/path
+ * <scheme>:/path
+ *
+ * For compatibility with previous behaviour it also accepts as an NFS scheme
+ * ip:/path
+ * /path
+ *
+ * If an ip is set it returns it in network byte order.
+ * The default scheme defined in the global netproto, if not set it defaults to
+ * NFS.
+ * It leaves just the pathname in the global rootpath.
  */
 uint32_t
 net_parse_rootpath()