staging: brcm80211: bugfix for 32 bit power pc platform

On some platforms resource_size_t == 64 but but unsigned long is only 32-bits.
In this particular problem, reported and fixed by Tony Breeds, a physical
address was truncated as a result.

Reported-by: Tony Breeds <tony@bakeyournoodle.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>