brcmfmac: use device memsize config from fw if defined

Newer type pcie devices have memory which get shared between fw and
hw. The division of this memory is done firmware compile time. As a
result the ramsize as used by driver needs to be adjusted for this.
This is done by reading the memory size from the firmware.

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