drm/panthor: flush FW AS caches in slow reset path

In the off-chance that waiting for the firmware to signal its booted status
timed out in the fast reset path, one must flush the cache lines for the
entire FW VM address space before reloading the regions, otherwise stale
values eventually lead to a scheduler job timeout.

Fixes: 647810ec ("drm/panthor: Add the MMU/VM logical block")
Cc: stable@vger.kernel.org
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240902130237.3440720-1-adrian.larumbe@collabora.com