brcmfmac: Register sizes on hardware are not dependent on compiler types

The 4 IO functions in this patch are incorrect as they use compiler types
to determine how many bytes to send to the hardware.

Signed-off-by: Ian Molton <ian@mnementh.co.uk>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>