powerpc: Simplify redundant Kconfig tests

PPC_85xx implies PPC32 so no need to check PPC32 in addition.

PPC64 && !PPC_BOOK3E_64 means PPC_BOOK3S_64.

PPC_BOOK3E_64 implies PPC_E500.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/244cce3e603f2b79796314c0c1c46cab927b9adc.1663606876.git.christophe.leroy@csgroup.eu