drm/i915: Use local variable for SSEU info in GETPARAM ioctl

drm/i915: Use local variable for SSEU info in GETPARAM ioctl

In the GETPARAM ioctl handler, use a local variable to consolidate
usage of SSEU runtime info.

v2: add const to sseu_dev_info variable

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190524154022.13575-2-stuart.summers@intel.com