powerpc/nohash: Refactor ptep_test_and_clear_young()

Remove ptep_test_and_clear_young() macro, make
__ptep_test_and_clear_young() common to nohash/32 and nohash/64
and change it to become ptep_test_and_clear_young()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/de90679ae169104fa3c98d0a8828d7ede228fc52.1695659959.git.christophe.leroy@csgroup.eu