powerpc: modules: change r2 save/restore offset for ELFv2 ABI.
powerpc: modules: change r2 save/restore offset for ELFv2 ABI.

ELFv2 uses a different stack offset (24 vs 40) to save r2.

Signed-off-by: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs