powerpc/8xxx: Fix possible compile issue related to P1013

The P1013 is a single core version of P1022 and thus should use the
p1022_serdes.c code.  It was acciently pointing to p1013_serdes.c which
doesn't exist.

Reported-by: Renaud Barbier <renaud.barbier@ge.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/cpu/mpc85xx/Makefile

@@ -89,7 +89,7 @@ COBJS-$(CONFIG_MPC8569) += mpc8569_serdes.o
 COBJS-$(CONFIG_MPC8572) += mpc8572_serdes.o
 COBJS-$(CONFIG_P1011)	+= p1021_serdes.o
 COBJS-$(CONFIG_P1012)	+= p1021_serdes.o
-COBJS-$(CONFIG_P1013)	+= p1013_serdes.o
+COBJS-$(CONFIG_P1013)	+= p1022_serdes.o
 COBJS-$(CONFIG_P1020)	+= p1021_serdes.o
 COBJS-$(CONFIG_P1021)	+= p1021_serdes.o
 COBJS-$(CONFIG_P1022)	+= p1022_serdes.o