powerpc/math-emu: Change types to work on ppc64

While normally we don't use the math emulation code on ppc64 it can be
useful for doing things like emulating the embedded FP instructions.

Since performance isn't critical in this scenario its easier to keep
the sizes of the various math-emu the same as on ppc32.

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