staging: brcm80211: use static qualifier for local symbols in brcmfmac

Cleanup resulted in merging several files and made several symbols
local to a source file. These were found by running sparse as it
gave the warning: symbol 'foo' was not declared. Should it be static?

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>