Revert "ath10k: QCA988X hw2.0: update firmware to 10.2.4.70.63-2"

This reverts commit c7370e2728.

10.2.4.70.63-2 was buggy and lots of people have been reporting crashes, Hauke
Mehrtens among others:

http://lists.infradead.org/pipermail/ath10k/2017-September/010138.html

This reverts the firmware back to 10.2.4.70.54.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

WHENCE

@@ -2686,7 +2686,7 @@ File: ath10k/QCA988X/hw2.0/firmware-4.bin
 Version: 10.2.4.45
 Licence: ath10k/QCA988X/hw2.0/notice_ath10k_firmware-4.txt
 File: ath10k/QCA988X/hw2.0/firmware-5.bin
-Version: 10.2.4.70.63-2
+Version: 10.2.4.70.54
 Licence: ath10k/QCA988X/hw2.0/notice_ath10k_firmware-5.txt
 File: ath10k/QCA6174/hw2.1/board.bin
 File: ath10k/QCA6174/hw2.1/board-2.bin