tegra: switch to kernel 5.4

Build the latest kernel by default, since testing did not show any
regressions.

Signed-off-by: Tomasz Maciej Nowak <tomek_n@o2.pl>
[fix merge conflict in tegra/Makefile]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/tegra/Makefile

@@ -13,7 +13,7 @@ FEATURES := audio boot-part display ext4 fpu gpio pci pcie rootfs-part rtc squas
 CPU_TYPE := cortex-a9
 CPU_SUBTYPE := vfpv3
 
-KERNEL_PATCHVER := 4.19
+KERNEL_PATCHVER := 5.4
 KERNEL_TESTING_PATCHVER := 5.4
 
 include $(INCLUDE_DIR)/target.mk