staging: brcm80211: removed duplicated file, linux_osl.c

Removed duplicated file, linux_osl.c from brcmfmac.
linux_osl.c under brcm80211/util/ will be shared
between softmac & fullmac drivers

Signed-off-by: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>