GCC 12 warnings in testsuite

[chrisj at rtems.org]

Hi

This patch fixes a number of easy warnings gcc 12 is now generating
in the testsuite.

There is a single addition of a pragma to silence a warning related.

The patch does not cover:

- Some fixes posted by Matt

- Two warnings related to a pointer returned by malloc

- Any warnings related to the validation tests. This is the notice there
  are issues in the validation tests that need to be sorted

Thanks
Chris