am33xx: refactor emif4/ddr to support multiple EMIF instances

The AM33xx emif4/ddr support closely matches what is need to support
TI814x except that TI814x has two EMIF instances. Refactor all the
emif4 helper calls and the config_ddr() init function to use an
additional instance number argument.

Signed-off-by: Matt Porter <mporter@ti.com>
Reviewed-by: Tom Rini <trini@ti.com>
diff --git a/board/phytec/pcm051/board.c b/board/phytec/pcm051/board.c
index 471725a..1708ac2 100644
--- a/board/phytec/pcm051/board.c
+++ b/board/phytec/pcm051/board.c
@@ -159,7 +159,7 @@
 	enable_board_pin_mux();
 
 	config_ddr(DDR_CLK_MHZ, MT41J256M8HX15E_IOCTRL_VALUE, &ddr3_data,
-			&ddr3_cmd_ctrl_data, &ddr3_emif_reg_data);
+			&ddr3_cmd_ctrl_data, &ddr3_emif_reg_data, 0);
 #endif
 }