Staging: fix Makefile so broadcom driver will actually build.

It would be nice if people tested their patches before sending
them to me...

Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Brett Rudley <brudley@broadcom.com>
Cc: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>