brcmfmac: Remove array of functions

Replace the array of functions with a pair of pointers to the
relevant functions.

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