drm/edid: make drm_edid_block_valid() static

drm_edid_block_valid() is no longer used outside of drm_edid.c. Make it
static.

Acked-by: Zhi Wang <zhiwang@kernel.rog>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812142849.1588006-2-jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>