uboot-mediatek: replace bootmenu shortkey patch with better version

uboot-mediatek: replace bootmenu shortkey patch with better version

Replace bootmenu shortmenu mediatek patch with a better version proposed
upstream that implement a more clean implementation.

Also the mediatek patch seems to be bugged and with lots of bootmenu
elements it's gets very bugged and unusable.

Refresh any affected patch.

Upstream-Status: Submitted [https://lore.kernel.org/u-boot/20250525134407[email protected]/]
Link: https://github.com/openwrt/openwrt/pull/18919
Signed-off-by: Christian Marangi <[email protected]>