powerpc/vdso: Remove lib32_elfinfo and lib64_elfinfo

lib32_elfinfo and lib64_elfinfo are not used anymore, remove them.

Also remove vdso32_kbase and vdso64_kbase while removing the
last use.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/01ac65abf22f0428f8f764525a7d84459c54d806.1601197618.git.christophe.leroy@csgroup.eu