drm/hdcp: reference for srm file format

In the kernel documentation, HDCP specifications links are shared as a
reference for SRM table format.

v2:
  Fixed small nits. [Shashank]
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/320968/?series=57232&rev=14

drivers/gpu/drm/drm_hdcp.c

@@ -271,6 +271,13 @@ static void drm_hdcp_request_srm(struct drm_device *drm_dev)
  *
  * SRM should be presented in the name of "display_hdcp_srm.bin".
  *
+ * Format of the SRM table, that userspace needs to write into the binary file,
+ * is defined at:
+ * 1. Renewability chapter on 55th page of HDCP 1.4 specification
+ * https://www.digital-cp.com/sites/default/files/specifications/HDCP%20Specification%20Rev1_4_Secure.pdf
+ * 2. Renewability chapter on 63rd page of HDCP 2.2 specification
+ * https://www.digital-cp.com/sites/default/files/specifications/HDCP%20on%20HDMI%20Specification%20Rev2_2_Final1.pdf
+ *
  * Returns:
  * TRUE on any of the KSV is revoked, else FALSE.
  */