omap5_uevm: Add CONFIG_SUPPORT_EMMC_BOOT, document usage

Add a README to the board which lists the commands required to enable
booting from the eMMC boot partitions found on the board.

Signed-off-by: Tom Rini <trini@ti.com>
Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>

board/ti/omap5_uevm/README

+Summary
+=======
+
+This document covers various features of the 'omap5_uevm' build and some
+related uses.
+
+eMMC boot partition use
+=======================
+
+It is possible, depending on SYSBOOT configuration to boot from the eMMC
+boot partitions using (name depending on documentation referenced)
+Alternative Boot operation mode or Boot Sequence Option 1/2.  In this
+example we load MLO and u-boot.img from the build into DDR and then use
+'mmc bootbus' to set the required rate (see TRM) and 'mmc partconfig' to
+set boot0 as the boot device.
+U-Boot # setenv autoload no
+U-Boot # usb start
+U-Boot # dhcp
+U-Boot # mmc dev 1 1
+U-Boot # tftp ${loadaddr} omap5uevm/MLO
+U-Boot # mmc write ${loadaddr} 0 100
+U-Boot # tftp ${loadaddr} omap5uevm/u-boot.img
+U-Boot # mmc write ${loadaddr} 300 400
+U-Boot # mmc bootbus 1 2 0 2
+U-Boot # mmc partconf 1 1 1 0

include/configs/omap5_uevm.h

@@ -37,6 +37,7 @@
 #define CONFIG_PARTITION_UUIDS
 #define CONFIG_CMD_PART
 #define CONFIG_HSMMC2_8BIT
+#define CONFIG_SUPPORT_EMMC_BOOT
 
 /* Required support for the TCA642X GPIO we have on the uEVM */
 #define CONFIG_TCA642X