meson-s4t7: Add option to force 16x9 display resolution

Description

Khadas's 5.4 kernel has a broken hdmi subsystem that can result into
a monitor not working even if it supports one of the required display
resolution. Hence adding a workaround that will force use of one of
the 3 16x9 resolutions supporting most of the HD-ready, full-HD and
4K monitors.

https://github.com/armbian/build/commit/2c8d5514229aa6e100905eb38c72877529c2ab84