staging: mt7621-pinctrl: remove unnecessary 'out of memory' message

Messages when memory allocation fails are not needed at all
and checkpatch script complains about them. Remove one in this
driver code.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>