Revert "ARM: mx6: add MMC2 boot device detection support in SPL"

Commit 54e4fcfa ("ARM: mx6: add MMC2 boot device detection
support in SPL") prevents UDOO neo board to boot:

Trying to boot from MMC2
port 1
MMC Device 1 not found
spl: could not find mmc device. error: -19
SPL: failed to boot from all boot devices

This reverts commit 54e4fcfa.

Signed-off-by: Breno Lima <breno.lima@nxp.com>

arch/arm/imx-common/spl.c

@@ -14,9 +14,6 @@
 #include <spl.h>
 
 #if defined(CONFIG_MX6)
-#define MX6_MMC_PORT_MASK	GENMASK(12, 11)
-#define MX6_MMC_PORT_2		BIT(11)
-
 /* determine boot device from SRC_SBMR1 (BOOT_CFG[4:1]) or SRC_GPR9 register */
 u32 spl_boot_device(void)
 {
@@ -58,11 +55,10 @@ u32 spl_boot_device(void)
 	/* SD/eSD: 8.5.3, Table 8-15  */
 	case 0x4:
 	case 0x5:
+		return BOOT_DEVICE_MMC1;
 	/* MMC/eMMC: 8.5.3 */
 	case 0x6:
 	case 0x7:
-		if ((reg & MX6_MMC_PORT_MASK) == MX6_MMC_PORT_2)
-			return BOOT_DEVICE_MMC2;
 		return BOOT_DEVICE_MMC1;
 	/* NAND Flash: 8.5.2 */
 	case 0x8 ... 0xf: