drm/i915/psr: report psr2 hw enabled from psr2_ctl

For PSR2 , as per spec, PSR2_CTL bit 31 to be set.
for psr1, bit 31 in SRD_CTL to be set. Reporting
"HW Enabled & Active bit" status for psr2 from SRD_CTL
gives  wrong status.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jim Bride <jim.bride@linux.intel.com>
Signed-off-by: vathsala nagaraju <vathsala.nagaraju@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481307129-29354-1-git-send-email-vathsala.nagaraju@intel.com