powerpc: Replace PPC_85xx || PPC_BOOKE_64 by PPC_E500

PPC_E500 is the same as PPC_85xx || PPC_BOOKE_64

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/af79696f8cb8536fb4e20c0d98a6bf159a9e371b.1663606876.git.christophe.leroy@csgroup.eu