linux-firmware: add frimware for mediatek bluetooth chip (MT7921)

Add binary firmware for MT7921 based devices

File: mediatek/BT_RAM_CODE_MT7961_1_2_hdr.bin
Version: 20210223142901
Signed-off-by: mark-yw.chen <mark-yw.chen@mediatek.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>

WHENCE

@@ -4932,6 +4932,15 @@ Version: 20210122002730
 
 Licence: Redistributable. See LICENCE.mediatek for details.
 
+--------------------------------------------------------------------------
+
+Driver: mt7921 - MediaTek MT7921 bluetooth chipset
+
+File: mediatek/BT_RAM_CODE_MT7961_1_2_hdr.bin
+Version: 20210223142901
+
+Licence: Redistributable. See LICENCE.mediatek for details.
+
 --------------------------------------------------------------------------
 Driver: nfp - Netronome Flow Processor