mvebu: switch to kernel 5.10

It's been brewing on my cortexa9 subtarget (Turris Omnia) for months.
Perfectly stable.

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
[modify subject to match previous updates]
Signed-off-by: Paul Spooren <mail@aparcar.org>

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
 SUBTARGETS:=cortexa9 cortexa53 cortexa72
 
-KERNEL_PATCHVER:=5.4
-KERNEL_TESTING_PATCHVER:=5.10
+KERNEL_PATCHVER:=5.10
 
 include $(INCLUDE_DIR)/target.mk