After recent changes on nuttx-apps (not limited to, but related
to nuttx-apps#2738, for instance), the stack usage for the NSH
task increased, causing stack overflows under specific situations
(when running `ps` command, for instance). This commit increases
the init task stack size to avoid it. Please note that, even before
these changes, the stack usage of the NSH task was around 90% and,
then, increasing the stack size of it was recommended.
a63c807353