drm/displayid: pass iter to drm_find_displayid_extension()

drm/displayid: pass iter to drm_find_displayid_extension()

It's more convenient to pass iter than a handful of its members to
drm_find_displayid_extension(), especially as we're about to add another
member.

Rename the function find_next_displayid_extension() while at it, to be
more descriptive.

Cc: Tiago Martins Araújo <tiago.martins.araujo@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Tiago Martins Araújo <tiago.martins.araujo@gmail.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/3837ae7f095e77a082ac2422ce2fac96c4f9373d.1761681968.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>