bcm53xx: add support for ASUS RT-AC3100

bcm53xx: add support for ASUS RT-AC3100

ASUS RT-AC3100 is ASUS RT-AC88U without the external switch.

OpenWrt forum users effortless and ktmakwana have confirmed that there are
revisions with either 4366b1 or 4366c0 wireless chips.

Therefore, include firmware for 4366b1 along with 4366c0. This way, all
hardware revisions of the router will be supported by having brcmfmac use
the firmware file for the wireless chip it detects.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
(cherry picked from commit 2214bab3503981fe6168746acd13044a9d5e89e7)