powerpc/configs: remove obsolete CONFIG_INET_XFRM_MODE_* and CONFIG_INET6_XFRM_MODE_*

These Kconfig options has been removed in commit 4c145dce

 ("xfrm:
make xfrm modes builtin") So there is no point to keep it in
defconfigs any longer.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
[mpe: Extract from cross arch patch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190612071901.21736-1-yuehaibing@huawei.com