powerpc: Copy default configs into arch/powerpc/configs

Copy default configs into arch/powerpc/configs, rename bpa_defconfig to
cell_defconfig while we're at it.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

diff --cc arch/powerpc/configs/cell_defconfig
Simple merge

diff --cc arch/powerpc/configs/g5_defconfig
Simple merge

diff --cc arch/powerpc/configs/iseries_defconfig
Simple merge

diff --cc arch/powerpc/configs/maple_defconfig
Simple merge

diff --cc arch/powerpc/configs/pseries_defconfig
Simple merge