Revert "Revert "mvebu: switch default kernel to 5.15""

This reverts commit 97c77fff28cf001399f33c7bc1ec6687ba18450b as commit
8be6350f6646 ("generic: 5.15: allow MV88E6xxx built-in when PTP support
disabled") contains the fix, so lets enable kernel 5.15 on mvebu again.

Signed-off-by: Petr Štetiar <[email protected]>

target/linux/mvebu/Makefile

@@ -9,8 +9,7 @@ BOARDNAME:=Marvell EBU Armada
 FEATURES:=fpu usb pci pcie gpio nand squashfs ramdisk boot-part rootfs-part legacy-sdcard targz
 SUBTARGETS:=cortexa9 cortexa53 cortexa72
 
-KERNEL_PATCHVER:=5.10
-KERNEL_TESTING_PATCHVER:=5.15
+KERNEL_PATCHVER:=5.15
 
 include $(INCLUDE_DIR)/target.mk