Staging: brcm80211: clean up makefile cflag lines

Change to use the proper ccflags-y option, as well as splitting the
options out one-per-line so that we can see what is needed to be cleaned
up and removed over time.

Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Nohee Ko <noheek@broadcom.com>
Cc: jason <jason@lakedaemon.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>