brcmfmac: use direct data pointer in NVRAM parser struct

As we plan to add support for platform NVRAM we should store direct
data pointer without the extra struct firmware layer. This will allow
us to support other sources with the only requirement being u8 buffer.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>