powerpc/32s: use CONFIG_PPC_BOOK3S_601 instead of reading PVR

Use CONFIG_PPC_BOOK3S_601 instead of reading PVR to know if
it is a 601 or not.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/909c26db9facd7fe454695b303f952e019dd9eda.1566834712.git.christophe.leroy@c-s.fr
2 files changed