selftests/powerpc: add const qualification where possible

Various char * parameters in the common powerpc selftest APIs can be
const.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230817-powerpc-selftest-misc-v1-2-a84cc1ef78b2@linux.ibm.com

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 191

Based on 1 normalized pattern(s):

licensed under gplv2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 99 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528170027.163048684@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

selftests/powerpc: Move shared headers into new include dir

There are some functions, especially register related, which can
be shared across multiple selftests/powerpc test directories.

This patch creates a new include directory to store those shared
files, so that the file layout becomes more neat.

Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
[mpe: Reworked to move the headers only]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>