mwifiex: add support for SD8987 chipset

This patch adds support for Marvell 88W8987 chipset with SDIO interface.
Register offsets and supported feature flags are updated. The corresponding
firmware image file shall be "mrvl/sd8987_uapsta.bin".

Signed-off-by: Tamás Szűcs <tszucs@protonmail.ch>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>