sunxi: switch to 5.4 kernel

Seems to be working fine on my a64-olinuxino, it's 99.9% upstream stuff
anyway. Lets start wider userbase testing.

Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/sunxi/Makefile

@@ -13,7 +13,7 @@ BOARDNAME:=Allwinner A1x/A20/A3x/R40
 FEATURES:=fpu usb ext4 display rtc squashfs
 SUBTARGETS:=cortexa8 cortexa7 cortexa53
 
-KERNEL_PATCHVER:=4.19
+KERNEL_PATCHVER:=5.4
 KERNEL_TESTING_PATCHVER:=5.4
 KERNELNAME:=zImage dtbs