drm/xe: Define IRQ offsets used by HW engines

When interrupts are delivered using memory based mechanism, engines
will write status to the report page at the offset (in bytes) that
corresponds to their interrupt bit from the GT_INTR_DW register.

Add engine interrupt offset definitions to engine info as we will
need this to process memory based interrupts.

Bspec: 46149, 50829, 50844
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20231214185955.1791-6-michal.wajdeczko@intel.com
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>