gpio: pl061: handle failed allocations

devm_kzalloc(), devm_kstrdup() and devm_kasprintf() all can
fail internal allocation and return NULL. Using any of the assigned
objects without checking is not safe. As this is early in the boot
phase and these allocations really should not fail, any failure here
is probably an indication of a more serious issue so it makes little
sense to try and rollback the previous allocated resources or try to
continue;  but rather the probe function is simply exited with -ENOMEM.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: 684284b6 ("ARM: integrator: add MMCI device to IM-PD1")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>