keystone: ddr3: add ddr3.h to hold ddr3 API

It's convinient to hold ddr3 function definitions in separate file
such as ddr3.h. So move this from hardware.h to ddr3.h.

Acked-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
diff --git a/board/ti/k2hk_evm/board.c b/board/ti/k2hk_evm/board.c
index ef90f9d..f910ebe 100644
--- a/board/ti/k2hk_evm/board.c
+++ b/board/ti/k2hk_evm/board.c
@@ -12,6 +12,7 @@
 #include <fdt_support.h>
 #include <libfdt.h>
 
+#include <asm/arch/ddr3.h>
 #include <asm/arch/hardware.h>
 #include <asm/arch/clock.h>
 #include <asm/io.h>
@@ -63,7 +64,7 @@
 
 int dram_init(void)
 {
-	init_ddr3();
+	ddr3_init();
 
 	gd->ram_size = get_ram_size((long *)CONFIG_SYS_SDRAM_BASE,
 				    CONFIG_MAX_RAM_BANK_SIZE);