ARM: AM43xx: EPOS_EVM: Add support for LPDDR2

AM4372 EPOS EVM has 1GB LPDDR2(Part no: MT42L256M32D2LG-25 WT:A)
Adding LPDDR2 init sequence and register details for the same.
Below is the brief description of LPDDR2 init sequence:
-> Configure VTP
-> Configure DDR IO settings
-> Disable initialization and refreshes until EMIF registers are programmed.
-> Program Timing registers
-> Program PHY control and Temp alert and ZQ config registers.
-> Enable initialization and refreshes and configure SDRAM CONFIG register
-> Wait till initialization is complete and the configure MR registers.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

arch/arm/include/asm/emif.h

@@ -14,11 +14,15 @@
 #define _EMIF_H_
 #include <asm/types.h>
 #include <common.h>
+#include <asm/io.h>
 
 /* Base address */
 #define EMIF1_BASE				0x4c000000
 #define EMIF2_BASE				0x4d000000
 
+#define EMIF_4D					0x4
+#define EMIF_4D5				0x5
+
 /* Registers shifts, masks and values */
 
 /* EMIF_MOD_ID_REV */
@@ -1148,6 +1152,14 @@ struct read_write_regs {
 	u32 write_reg;
 };
 
+static inline u32 get_emif_rev(u32 base)
+{
+	struct emif_reg_struct *emif = (struct emif_reg_struct *)base;
+
+	return (readl(&emif->emif_mod_id_rev) & EMIF_REG_MAJOR_REVISION_MASK)
+		>> EMIF_REG_MAJOR_REVISION_SHIFT;
+}
+
 /* assert macros */
 #if defined(DEBUG)
 #define emif_assert(c)	({ if (!(c)) for (;;); })