drm/rockchip: dw-mipi-dsi: don't configure hardware in mode_set for MIPI

With atomic modesetting the hardware will be powered off when the
mode_set function is called.  We should configure the hardware in the
enable function, which is the atomic version of "commit" so let's use
the enable hook rather than commit while we're at it.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170224125506.21533-2-john@metanate.com