clk: sunxi-ng: h6-r: Simplify R_APB1 clock definition

Like the APB0 clock on previous chips, this is a simple single-parent
clock with an M divider. Use the equivalent helper macro instead of
writing out the whole clock description manually.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>