rbd: check snap_count against RBD_MAX_SNAP_COUNT

rbd: check snap_count against RBD_MAX_SNAP_COUNT

snap_count is u32 but the comparison is against a SIZE_MAX-derived value
(~2^61 on 64-bit), which clang flags as always false with
-Wtautological-constant-out-of-range-compare.

The proper check here should be that snap_count does not go over
RBD_MAX_SNAP_COUNT.

Assisted-by: Opencode:Big-pickle
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Alex Elder <elder@riscstar.com>
Link: https://patch.msgid.link/20260530011255.52916-1-rosenp@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>