ath79: switch default kernel to 6.1

The 6.1 kernel has been tested for over half a year.

Signed-off-by: Shiji Yang <[email protected]>

target/linux/ath79/Makefile

@@ -8,8 +8,7 @@ SUBTARGETS:=generic mikrotik nand tiny
 
 FEATURES:=ramdisk squashfs usbgadget
 
-KERNEL_PATCHVER:=5.15
-KERNEL_TESTING_PATCHVER:=6.1
+KERNEL_PATCHVER:=6.1
 
 include $(INCLUDE_DIR)/target.mk