linux-postmarketos-amlogic: upgrade to 6.4, get rid of KII Pro patches

This merge request upgrades the linux kernel used on Amlogic devices to version 6.4.

KII Pro device tree patches have been dropped as they're now in mainline:

• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/boot/dts/amlogic/meson-gxbb-kii-pro.dts?id=815ad625ec4ea5de655f9c02ccf7f65ecf5e6e29
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/boot/dts/amlogic/meson-gxbb-kii-pro.dts?id=dae485f52a65ce939b045cf480c401d434cacf2d
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/boot/dts/amlogic/meson-gxbb-kii-pro.dts?id=914a3aa644cf50947a2dbb97738502ca9f025a10

V=1 got removed as it's unnecessary now.

Cc: @phodina, @exkc, @craftyguy