PM / clk: Remove error message on out-of-memory condition

There is no need to print an error message if kstrdup() fails, as the
memory allocation core already takes care of that.

Note that commit 59d84ca8 ("PM / OPP / clk: Remove unnecessary
OOM message") already removed similar error messages, but this one was
forgotten.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>