clk: Add missing clk_core_init_rate_req calls

Some callers of clk_core_round_rate_nolock() will initialize the
clk_rate_request structure by hand, missing a few parameters that leads
to inconsistencies in what drivers can expect from that structure.

Let's use clk_core_init_rate_req() everywhere to make sure it's built in
a consistent manner.

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # imx8mp
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> # exynos4210, meson g12b
Signed-off-by: Maxime Ripard <maxime@cerno.tech>