clk: sunxi-ng: gate: Add macros for gates with fixed dividers

It is possible to declare a gate with a fixed divider, by using the
CCU_FEATURE_ALL_PREDIV flag. Since this is not obvious, add a macro
for declaring this type of clock.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20211119043545.4010-6-samuel@sholland.org