brcmfmac: obtain feature info using 'cap' firmware command

Several features in the driver directly map to a firmware feature
listed in response of the 'cap' firmware command. For those features
this response will be examined instead of attempting individual
firmware commands.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Mathy Vanhoef <vanhoefm@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>