linux-firmware: add version 2 for MT7615E

Update version to 20200131:
- use tag sta_rec_wtbl to replace legacy MCU_EXT_CMD_WTBL_UPDATE command.
- Fix firmware header version number.

Note that this version keeps legacy way for backward compatibility.
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>

WHENCE

@@ -4473,7 +4473,7 @@ Licence: Redistributable. See LICENCE.mediatek for details.
 Driver: mt7615e - MediaTek MT7615e Wireless MACs
 
 File: mediatek/mt7615_n9.bin
-Version: 20190114
+Version: 20200131
 File: mediatek/mt7615_cr4.bin
 Version: 20190114
 File: mediatek/mt7615_rom_patch.bin