drm/i915/gen9: Always set mask memory up when enabling DC5 or DC6

Move call to gen9_set_dc_state_debugmask_memory_up() into
gen9_set_dc_state() to prevent us missing it somewhere.

Signed-off-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1447084107-8521-3-git-send-email-patrik.jakobsson@linux.intel.com