[POWERPC] Created arch/powerpc/platforms/Kconfig for "Platform support"

Split "Platform support" menu out from arch/powerpc/Kconfig into
arch/powerpc/platforms/Kconfig in prep for allowing other sub-arches to
be configured via a single "Platform support" menu.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
2 files changed