broadcom-wl: simplify processing of 'hwmode'

Default gmode to "GOnly" unless explicitly overwridden.  This corrects
processing for 11ng to specify "GOnly" for gmode instead of "Auto"
(which translated to "bg").

Signed-off-by: Nathan Hintz <nlhintz@hotmail.com>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38754 3c298f89-4303-0410-b956-a3cf2f4a3e73