[POWERPC] iSeries: Merge vpdinfo.c into pci.c

There was only one global function in vpdinfo.c and it was only called
from pci.c, so merge them and make the function static.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>