drm/msm/submit: fix overflow check on 64-bit architectures

The overflow check does causes a warning from clang-14 when 'sz' is a type
that is smaller than size_t:

drivers/gpu/drm/msm/msm_gem_submit.c:217:10: error: result of comparison of constant 18446744073709551615 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
                if (sz == SIZE_MAX) {

Change the type accordingly.

Fixes: 20224d71

 ("drm/msm/submit: Move copy_from_user ahead of locking bos")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20210927113632.3849987-1-arnd@kernel.org
Signed-off-by: Rob Clark <robdclark@chromium.org>