drm/panthor: clean up some types in panthor_sched_suspend()

These variables should be u32 instead of u64 because they're only
storing u32 values.  Also static checkers complain when we do:

	suspended_slots &= ~upd_ctx.timedout_mask;

In this code "suspended_slots" is a u64 and "upd_ctx.timedout_mask".  The
mask clears out the top 32 bits which would likely be a bug if anything
were stored there.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
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/85356b15-4840-4e64-8c75-922cdd6a5fef@moroto.mountain