brcmfmac: Add support for CYW4373 SDIO/USB chipset

Add support for CYW4373 SDIO/USB chipset.
CYW4373 is a 1x1 dual-band 11ac chipset with 20/40/80Mhz channel support.
It's a WiFi/BT combo device.

Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>