clk: sunxi: Add apb0 gates for H3

This patch adds support for APB0 in H3. It seems to be compatible with
earlier SOCs. apb0 gates controls R_ block peripherals (R_PIO, R_IR,
etc).

Since this gates behave just like any Allwinner clock gate, add a generic
compatible that can be reused if we don't have any clock to protect.

Signed-off-by: Krzysztof Adamski <k@japko.eu>
[Maxime: Removed the H3 compatible from the simple-gates driver, reworked
         the commit log a bit]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>