drm/xe/guc: Allow CTB G2H processing without G2H IRQ

drm/xe/guc: Allow CTB G2H processing without G2H IRQ

During early initialization, in the xe_guc_min_load_for_hwconfig()
function, we are successfully enabling CTB communication, but it
will only allow us to send non-blocking H2G messages, as due to
not yet enabled IRQs, including G2H IRQs, we will not notice any
new G2H message sent by the GuC, including replies to our blocking
H2G request messages. And those successful replies are mandatory
for the VF drivers to continue normal operations.

As attempt to workaround this driver initialization ordering issue,
introduce special safe-mode CTB worker, that will periodically
trigger G2H processing, like original IRQ handler, in case no
MSI/MSIX IRQs were enabled on the driver yet. Once we detect that
IRQ were enabled, we will stop this worker.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240606130639.1504-3-michal.wajdeczko@intel.com