staging: brcm80211: replace BUS_SWAP32 macro with cpu_to_le32()

The macro BUS_SWAP32(a) expanded to (a) which was fine for a little
endian system. For big endian platform this should do as the name
implies. As the driver is intended for PCI which is little-endian
the macro cpu_to_le32() can be used instead.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>