clk: update clk_clean_rate_cache to use private clk struct

In clk_clean_rate_cache, clk->rate should update the private clock
struct, in particular when CCF is activated, to save the cached
rate value.

When clk_get_parent_rate is called, the cached information
is read from pclk->rate, with pclk = clk_get_parent(clk).

As the cached is read from private clk data, the update should
be done also on it.

Fixes: 6b7fd312 ("clk: fix set_rate to clean up cached rates for the hierarchy")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Link: https://lore.kernel.org/r/20220620153717.v2.1.Ifa06360115ffa3f3307372e6cdd98ec16759d6ba@changeid
Link: https://lore.kernel.org/r/20220712142352.RESEND.v2.1.Ifa06360115ffa3f3307372e6cdd98ec16759d6ba@changeid/