i2c: designware: Don't warn about missing get_clk_rate_khz

Converting the WARN_ON() to a dev_dbg() message in
i2c_dw_clk_rate().

That removes the need to supply a dummy implementation for
the callback (or alternatively a dummy clk device) when the
fallback path is preferred where the existing values already
in the clock registers are used - when a firmware has
programmed the clock registers.

The fallback path was introduced in commit 4fec76e
("i2c: designware: Fix wrong setting for {ss,fs,hs}_{h,l}cnt
registers").

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20250513124015.2568924-1-heikki.krogerus@linux.intel.com
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Author: Heikki Krogerus

drivers/i2c/busses/i2c-designware-common.c

@@ -572,8 +572,10 @@ u32 i2c_dw_clk_rate(struct dw_i2c_dev *dev)
 	 * Clock is not necessary if we got LCNT/HCNT values directly from
 	 * the platform code.
 	 */
-	if (WARN_ON_ONCE(!dev->get_clk_rate_khz))
+	if (!dev->get_clk_rate_khz) {
+		dev_dbg_once(dev->dev, "Callback get_clk_rate_khz() is not defined\n");
 		return 0;
+	}
 	return dev->get_clk_rate_khz(dev);
 }