gemini: Bump kernel to v5.4

The v5.4 kernel already works much better than v4.19
as so many things got upstreamed so let's just bump
it to kernel v5.4.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

target/linux/gemini/Makefile

@@ -12,7 +12,7 @@ BOARDNAME:=Cortina Systems CS351x
 FEATURES:=squashfs pci rtc usb dt gpio display ext4 rootfs-part boot-part
 CPU_TYPE:=fa526
 
-KERNEL_PATCHVER:=4.19
+KERNEL_PATCHVER:=5.4
 
 define Target/Description
 	Build firmware images for the StorLink/Cortina Gemini CS351x ARM FA526 CPU