bcm27xx: switch to 5.4 kernel

Been running it for a few days on RPi0W PMS sensor node and on RPi4.
Lets start wider userbase testing.

Cc: Stijn Tintel <stijn@linux-ipv6.be>
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/bcm27xx/Makefile

@@ -14,8 +14,7 @@ FEATURES:=ext4 audio usb usbgadget display gpio fpu squashfs rootfs-part boot-pa
 MAINTAINER:=Álvaro Fernández Rojas <noltari@gmail.com>
 SUBTARGETS:=bcm2708 bcm2709 bcm2710 bcm2711
 
-KERNEL_PATCHVER:=4.19
-KERNEL_TESTING_PATCHVER=5.4
+KERNEL_PATCHVER=5.4
 
 define Target/Description
 	Build firmware image for Broadcom BCM27xx SoC devices.