tools/tplink-safeloader: use soft_ver 1.9.1 for archer c6 v2

TP-LINK published a firmware update for the archer c6 v2.
This updates also reached the factory devices. Newer software version
rejects downgrading to 1.2.x. Use 1.9.x to allow installing the factory images
and have a little bit time to change it again.

Tested on archer c6 v2 with firmware 1.3.1

Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
(cherry picked from commit 6d5d815e3f6850a0dc754bf16053fa34490766f7)

tools/firmware-utils/src/tplink-safeloader.c

@@ -710,7 +710,7 @@ static struct device_info boards[] = {
 			"{product_name:Archer C6,product_ver:2.0.0,special_id:52550000}\r\n"
 			"{product_name:Archer C6,product_ver:2.0.0,special_id:4A500000}\r\n",
 		.support_trail = '\x00',
-		.soft_ver = "soft_ver:1.2.1\n",
+		.soft_ver = "soft_ver:1.9.1\n",
 
 		.partitions = {
 			{"fs-uboot", 0x00000, 0x20000},