drm/intel: add enable_psr module option and disable psr by default

v2: prefer seq_puts to seq_printf detected by Paulo Zanoni.
v3: PSR is disabled by default. Without userspace ready it
    will cause regression for kde and xdm users

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 973f272..9d871c7 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1565,6 +1565,9 @@
 		case PSR_NO_SINK:
 			seq_puts(m, "not supported by panel");
 			break;
+		case PSR_MODULE_PARAM:
+			seq_puts(m, "disabled by flag");
+			break;
 		case PSR_CRTC_NOT_ACTIVE:
 			seq_puts(m, "crtc not active");
 			break;