staging: brcm80211: deleted two fullmac source files

Having both a 'generic' as a 'linux' specific variant of a file makes
no sense in a Linux environment. Merged bcmsdh_sdmmc_linux.c into
bcmsdh_sdmmc.c, and bcmsdh_linux.c into bcmsdh.c.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>