mvebu: add kernel 6.1 as testing kernel

With an initial set of patches and configs in place let's start testing
with kernel 6.1.

Run-tested on the cortexa9 subtarget (WRT1900ACS, Turris Omnia)

Tested-by: Etienne Champetier <[email protected]>
Signed-off-by: Stefan Kalscheuer <[email protected]>

target/linux/mvebu/Makefile

@@ -10,6 +10,7 @@ FEATURES:=fpu usb pci pcie gpio nand squashfs ramdisk boot-part rootfs-part lega
 SUBTARGETS:=cortexa9 cortexa53 cortexa72
 
 KERNEL_PATCHVER:=5.15
+KERNEL_TESTING_PATCHVER:=6.1
 
 include $(INCLUDE_DIR)/target.mk