staging: brcm80211: replaced prefix of SDIO related functions

Code cleanup. Prefixed functions with brcmf_ for unique namespace. In addition
to that, prefix has been changed to categorize functions depending on their
place in the drivers SDIO stack.

Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>