drm: Add DP PSR2 sink enable bit

BugLink: https://bugs.launchpad.net/bugs/1791953

[ Upstream commit 4f212e40 ]

To comply with eDP1.4a this bit should be set when enabling PSR2.
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180328223046.16125-1-jose.souza@intel.comSigned-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

include/drm/drm_dp_helper.h

@@ -342,6 +342,7 @@
 # define DP_PSR_FRAME_CAPTURE		    (1 << 3)
 # define DP_PSR_SELECTIVE_UPDATE	    (1 << 4)
 # define DP_PSR_IRQ_HPD_WITH_CRC_ERRORS     (1 << 5)
+# define DP_PSR_ENABLE_PSR2		    (1 << 6) /* eDP 1.4a */
 
 #define DP_ADAPTER_CTRL			    0x1a0
 # define DP_ADAPTER_CTRL_FORCE_LOAD_SENSE   (1 << 0)