KVM: PPC: Kconfig: Fix indentation

The convention for indentation seems to be a single tab. Help text is
further indented by an additional two whitespaces. Fix the lines that
violate these rules.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220520115431.147593-1-juergh@canonical.com