powerpc: Add 64-bit CPU targets for gcc

Add a menu to select various 64-bit CPU targets for gcc. We
default to -mtune=power7 and if gcc doesn't understand that we
fallback to -mtune=power4.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2 files changed