drm/probe-helper: Add drm_crtc_helper_mode_valid_fixed()

Add drm_crtc_helper_mode_valid_fixed(), which validates a given mode
against a display hardware's mode. Convert simpledrm and use it in a
few other drivers with static modes.

v4:
	* remove empty line after opening brace
v2:
	* rename 'static' and 'hw' to 'fixed' everywhere

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220905141648.22013-3-tzimmermann@suse.de