powerpc/mpc8xxx: Add memory reset control

JEDEC spec requires the clocks to be stable before deasserting reset
signal for RDIMMs. Clocks start when any chip select is enabled and
clock control register is set. This patch also adds the interface to
toggle memory reset signal if needed by the boards.

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/arch/powerpc/cpu/mpc8xxx/ddr/ddr.h b/arch/powerpc/cpu/mpc8xxx/ddr/ddr.h
index 4dd55fc..c173a5a 100644
--- a/arch/powerpc/cpu/mpc8xxx/ddr/ddr.h
+++ b/arch/powerpc/cpu/mpc8xxx/ddr/ddr.h
@@ -96,7 +96,7 @@
 
 /* processor specific function */
 void fsl_ddr_set_memctl_regs(const fsl_ddr_cfg_regs_t *regs,
-				   unsigned int ctrl_num);
+				   unsigned int ctrl_num, int step);
 
 /* board specific function */
 int fsl_ddr_get_dimm_params(dimm_params_t *pdimm,