target-ppc: Inline comma into POWERPC_DEF_SVR() macro

To repurpose the POWERPC_DEF_SVR() macro outside of an array,
move the comma into the macro. No functional change.

Signed-off-by: Andreas Färber <afaerber@suse.de>
target-ppc: Extract aliases

Signed-off-by: Andreas Färber <afaerber@suse.de>
target-ppc: Convert CPU definitions

Signed-off-by: Andreas Färber <afaerber@suse.de>