clk: imx: clk-gpr-mux: Provide clock name in error message

In error case the error message doesn't provide much context:

imx:clk-gpr-mux: failed to get parent (-EINVAL)

So additionally provide the clock name in the message, in
order to simplify the further analyze.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20230308184603.10049-1-stefan.wahren@i2se.com