drm/probe-helper: Call connector detect functions in single helper

Move the logic to call the connector's detect helper into a single
internal function. Reduces code dupliction.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240715093936.793552-2-tzimmermann@suse.de