drm/ast: astdp: Simplify power management when detecting display

Remove the CRTC handling in the ASTDP detect_ctx helper and enable
power while the detecting the display. Unconditionally wait a few
milliseconds after switching power. Simplifies the code and makes it
more robust.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240815151953.184679-6-tzimmermann@suse.de