bluetooth: controller: Reduce user ops status to uint8_t

The status field is currently a uint32_t even though there are only
3 possible values. Reducing it to a uint8_t allows status to fit in
existing padding in the struct, saving 4 bytes per ticker_user_op

Updated function signatures to match; ticker_op_func left as-is
to avoid having to update a whole bunch of files for no real benefit

Signed-off-by: Troels Nilsson <trnn@demant.com>