clk: sunxi-ng: h6-r: Fix AR100/R_APB2 parent order
According to the BSP source code, both the AR100 and R_APB2 clocks have
PLL_PERIPH0 as mux index 3, not 2 as it was on previous chips. The pre-
divider used for PLL_PERIPH0 should be changed to index 3 to match.
This was verified by running a rough benchmark on the AR100 with various
clock settings: