powerpc/machdep: Move sys_ctrler_t definition into pmac_feature.h

sys_ctrler_t definitions are tied to pmac. Move it into pmac_feature.h

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Move to pmac_feature.h to fix some build errors]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7dd5ead4bbca749e2da089ff6fe2b1878d6bf40e.1630667612.git.christophe.leroy@csgroup.eu