i915/drrs/debugfs: psr status info addition

Existing debugfs entry i915_drrs_status is updated with whether PSR
is the cause for DRRS disabled state.

[v2]: Dropped the module parameter details as ctl moved from module
      parameter to debugfs. [Rodrigo]

[v3]: Crtc ID information is dropped as there is no immediate usecase.
      [Rodrigo].

Signed-off-by: C, Ramalingam <ramalingam.c@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/1511151827-6596-1-git-send-email-ramalingam.c@intel.com