ath10k-firmware: update firmware version for QCA988X

Updates the ath10k firmware version for QCA988X to version
10.2.4.70.10-2, which appears to fix problems with the 5GHz wireless
failing on TP-Link Archer C7 v2 when using a Nexus 5X phone. Fixes
issue #20854.

Signed-off-by: Robert Hancock <hancockrwd@gmail.com>

SVN-Revision: 47454