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: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NAlexander Graf <agraf@suse.de>