at91: set 6.1 as default kernel version

Adjust the kernel version to default 6.1 in order to facilitate testing
for a broader audience.

Signed-off-by: Nick Hainke <[email protected]>

target/linux/at91/Makefile

@@ -10,8 +10,7 @@ BOARDNAME:=Microchip (Atmel AT91)
 FEATURES:=ext4 squashfs targz usbgadget ubifs
 SUBTARGETS:=sama7 sama5 sam9x
 
-KERNEL_PATCHVER:=5.15
-KERNEL_TESTING_PATCHVER:=6.1
+KERNEL_PATCHVER:=6.1
 
 include $(INCLUDE_DIR)/target.mk