clk: clk-mux: Delete an error message for a failed memory allocation

Omit an extra message for a memory allocation failure in this function.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
[sboyd@codeaurora.org: Cleanup commit text]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>