powerpc: Fix off-by-one error in prom_init.c

This was preventing us from recognizing that we did actually
instantiate RTAS successfully on pSeries.

Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/kernel/prom_init.c

···
 
 	if (rets != NULL)
 		for (i = 1; i < nret; ++i)
-			rets[i] = args.args[nargs+i];
+			rets[i-1] = args.args[nargs+i];
 
 	return (nret > 0) ? args.args[nargs] : 0;
 }