drm/modes: Allow DRM_MODE_ROTATE_0 when applying video mode parameters

At the moment, only DRM_MODE_ROTATE_180 is allowed when we try to apply
the rotation from the video mode parameters. It is also useful to allow
DRM_MODE_ROTATE_0 in case there is only a reflect option in the video mode
parameter (e.g. video=540x960,reflect_x).

DRM_MODE_ROTATE_0 means "no rotation" and should therefore not require
any special handling, so we can just add it to the if condition.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200117153429.54700-3-stephan@gerhold.net