gpio: em: Remove error messages on out-of-memory conditions

There is no need to print error messages when memory allocations or
related operations fail, as the core will take care of that.

Change the returned error codes to -ENOMEM to match the failure cause
while at it.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>