package/gst1-vaapi: fix x11 dependencies

The x11 feature needs libx11 and libxrandr support.

Select and depend on these when x11 is enabled.

Fixes:
gst1-vaapi-1.22.0/meson.build:96:0: ERROR: Dependency "xrandr" not found, tried pkgconfig and cmake

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>