clk: rockchip: Add a mux flag to select the closest parent

[manu]

Summary

Add RK_CLK_MUX_ROUND_PARENT for muxes whose parents are fixed rate clocks
that can be shared with other consumers. When a rate is requested, pick
the parent with the rate that best fits the rounding flags and never change
the rate of a parent. Without it the request is passed up to the shared
parents, which refuse to change.

[mmel]

sys/dev/clk/rockchip/rk_clk_mux.c

178

AI, welcome:) Shoul be "round = CLK_SET_ROUND(flags);"

184

This is ugly and searching by name on the system with a few hundred or thousand clocks can be very slow.
We needed something like clknode_get_parent_by_idx(clk, idx). I'll do it later.

191

if (round == CLK_SET_ROUND_EXAC && pfreq != *fout))

192

round == CLK_SET_ROUND_EXAC

[manu]

Update patch