[POWERPC] iseries: Fix a compiler warning in platforms/iseries/vpdinfo.c

iSeries_Get_Location_Code() has error paths, but currently returns void, so
give it a return code and only print the output if it returns successfully.
Gcc isn't smart enough to be quiet though, so set frame to 0 to shut it up.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>