mwlwifi: downgrade the 88W8964's firmware to 9.3.2.6

Avoid 88W8964 firmware 9.3.2.12 for Wi-Fi instabilities it causes on Linksys WRT3200ACM & WRT32X until fixes on master branch are backported to openwrt-21.02

Signed-off-by: Arınç ÜNAL <arinc.unal@gmail.com>

package/kernel/mwlwifi/Makefile

@@ -15,9 +15,9 @@ PKG_LICENSE_FILES:=
 
 PKG_SOURCE_URL:=https://github.com/kaloz/mwlwifi
 PKG_SOURCE_PROTO:=git
-PKG_SOURCE_DATE:=2020-02-06
-PKG_SOURCE_VERSION:=a2fd00bb74c35820dfe233d762690c0433a87ef5
-PKG_MIRROR_HASH:=0eda0e774a87e58e611d6436350e1cf2be3de50fddde334909a07a15b0c9862b
+PKG_SOURCE_DATE:=2019-08-18
+PKG_SOURCE_VERSION:=747796b2f126df01c3c5442c607b4ea0497b1c6c
+PKG_MIRROR_HASH:=11985b8132edd1db1001748b0fc6d915205b7bcaf2a7512a4befb5ef3cc83bb9
 
 PKG_MAINTAINER:=Imre Kaloz <kaloz@openwrt.org>
 PKG_BUILD_PARALLEL:=1