drm/i915/gsc: skip irq initialization if using polling

drm/i915/gsc: skip irq initialization if using polling

Some platforms require the host to poll on the
GSC registers instead of relaying on the interrupts.
For those platforms, irq initialization should be skipped

Signed-off-by: Vitaly Lubart <vitaly.lubart@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220907215113.1596567-2-tomas.winkler@intel.com
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>