drm/i915/gen9_lp: Increase DDI PHY0 power well enabling timeout

drm/i915/gen9_lp: Increase DDI PHY0 power well enabling timeout

On GLK sporadic timeouts occur during PHY0 enabling. Based on logs it looks
like they happen sometime after a system suspend/resume cycle, with the
same power well enabling succeeding both before and after the failed
one and no other problems observed. The current timeout in the code is
not actually specified by BSpec, so let's try to increase that until a
BSpec update.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105771
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180409122716.4055-1-imre.deak@intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>