cmd: clk: probe the clock before dump them

The clock UCLASS need to be probed to allow availability of the
private data (struct clk *), get in show_clks() with dev_get_clk_ptr()
before use them.

Without this patch the clock dump can cause crash because all the
private data are not available before calling the API clk_get_rate().

It is the case for the SCMI clocks, priv->channel is needed for
scmi_clk_get_rate() and it is initialized only in scmi_clk_probe().
This issue causes a crash for "clk dump" command on STM32MP135F-DK board
for SCMI clock not yet probed.

Fixes: 1a725e22 ("clk: fix clock tree dump to properly dump out every registered clock")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Link: https://lore.kernel.org/r/20221213145708.v2.1.Ia0bc6b272f1e2e3f37873c61d79138c2663c4055@changeid