am335x: fix GPMC config for NAND and NOR SPL boot

GPMC controller is common IP to interface with both NAND and NOR flash devices.
Also, it supports max 8 chip-selects, which can be independently connected to
any of the devices.
But ROM code expects the boot-device to be connected to only chip-select[0].
Thus to resolve conflict between NOR and NAND boot. This patch:
- combines NOR and NAND configs spread in board files to common gpmc_init()
- configures GPMC based on boot-mode selected for SPL boot.

Signed-off-by: Pekon Gupta <pekon@ti.com>

board/ti/am335x/board.c

@@ -481,26 +481,14 @@ void sdram_init(void)
  */
 int board_init(void)
 {
-#ifdef CONFIG_NOR
-	const u32 gpmc_nor[GPMC_MAX_REG] = { STNOR_GPMC_CONFIG1,
-		STNOR_GPMC_CONFIG2, STNOR_GPMC_CONFIG3, STNOR_GPMC_CONFIG4,
-		STNOR_GPMC_CONFIG5, STNOR_GPMC_CONFIG6, STNOR_GPMC_CONFIG7 };
-#endif
-
 #if defined(CONFIG_HW_WATCHDOG)
 	hw_watchdog_init();
 #endif
 
 	gd->bd->bi_boot_params = CONFIG_SYS_SDRAM_BASE + 0x100;
-
+#if defined(CONFIG_NOR) || defined(CONFIG_NAND)
 	gpmc_init();
-
-#ifdef CONFIG_NOR
-	/* Reconfigure CS0 for NOR instead of NAND. */
-	enable_gpmc_cs_config(gpmc_nor, &gpmc_cfg->cs[0],
-			      CONFIG_SYS_FLASH_BASE, GPMC_SIZE_16M);
 #endif
-
 	return 0;
 }