Move the DPOunit clock gate workaround to directly after the PLL enable.

The exact location of the workaround does not matter and there are 2
reasons to group it with the PLL enable:

1) This moves it out of the middle of the init sequence from the spec,
   making it easier to follow the init sequence / compare it to the spec

2) It is grouped with the pll disable call in intel_dsi_post_disable,
   so for consistency it should be grouped with the pll enable in
   intel_dsi_pre_enable
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1488374106-4949-5-git-send-email-jani.nikula@intel.com