drm/panfrost: Don't rework job IRQ enable mask in the enable path

drm/panfrost: Don't rework job IRQ enable mask in the enable path

Up until now, panfrost_job_enable_interrupts() would always recalculate the
same job IRQ enablement mask, which is effectively a constant.

Replace it with a compile-time constant value, and also in another couple
places where an equivalent expression was being used.

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Link: https://lore.kernel.org/r/20251019145225.3621989-8-adrian.larumbe@collabora.com
Signed-off-by: Steven Price <steven.price@arm.com>