drm/i915/psr: Avoid PSR exit max time timeout

Specification requires that max time should be masked from bdw and
forward but it can be also safely enabled to hsw.
This will make PSR exits more deterministic and only when really
needed. If this was used to fix a issue in some panel than can
only self-refresh for a few seconds, that panel will interrupt
and assert one of the PSR errors handled in:
'drm/i915/psr: Handle PSR RFB storage error' and
'drm/i915/psr: Begin to handle PSR/PSR2 errors set by sink'

Spec: 21664

v4:
patch moved to before 'drm/i915/psr/bdw+: Enable CRC check in the
static frame on the sink side' to avoid touch in 2 patches
EDP_PSR_DEBUG.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180626201644.21932-4-jose.souza@intel.com

drivers/gpu/drm/i915/intel_psr.c

@@ -579,7 +579,8 @@ static void intel_psr_enable_source(struct intel_dp *intel_dp,
 			   EDP_PSR_DEBUG_MASK_MEMUP |
 			   EDP_PSR_DEBUG_MASK_HPD |
 			   EDP_PSR_DEBUG_MASK_LPSP |
-			   EDP_PSR_DEBUG_MASK_DISP_REG_WRITE);
+			   EDP_PSR_DEBUG_MASK_DISP_REG_WRITE |
+			   EDP_PSR_DEBUG_MASK_MAX_SLEEP);
 	}
 }