drm/edid: make drm_edid_are_equal() more convenient for its single user

drm/edid: make drm_edid_are_equal() more convenient for its single user

Repurpose drm_edid_are_equal() to be more helpful for its single user,
and rename drm_edid_eq(). Functionally deduce the length from the blob
size, not the blob data, making it more robust against any errors.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1011a285d30babce3aabd8218abb7ece7dcf58a2.1713259151.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>