boards/xtensa: Skip cleaning intermediate binaries up

This commit removes `CONFIG_CLEANUP_INTERMEDIATE_FILES` y-selection from
some Xtensa board configs. Y-selecting this option causes `west spdx` to
fail, due to reasons described in `CONFIG_CLEANUP_INTERMEDIATE_FILES` help
string.

If CLEANUP_INTERMEDIATE_FILES is y-selected, build files are removed from
the `cfgTarget.target.artifacts` list. This in turn causes the
`addBuildFile` function to nod add them to `pkg`, so `pkg.targetBuildFile`
is `None` in `scripts/west_commands/zspdx/walker.py`. This causes the `west
spdx` command to fail.

Signed-off-by: Kamil Galik <kgalik@internships.antmicro.com>
Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>