tests/kernel: Disable -Werror when testing deprecated pipe APIs

These two tests are validating that deprecated APIs still work
correctly. Which means they will definitely generate compile warnings.

To disable -Werror while letting it be enabled for other tests, create a
new Kconfig variable, DEPRECATION_TEST and make
COMPILER_WARNINGS_AS_ERRORS depend on that option being unselected. Add
this option to the two tests so that the resulting configuration
disables -Werror.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>