clk: renesas: rcar-gen2: Delete error message for failed memory allocation

The script "checkpatch.pl" pointed information out like the following.

WARNING: Possible unnecessary 'out of memory' message

Thus fix affected source code places.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>