fastboot: handle flash write to GPT partitions

Implement a feature to allow fastboot to write the downloaded image
to the space reserved for the Protective MBR and the Primary GUID
Partition Table.
Additionally, prepare and write the Backup GUID Partition Table.

Signed-off-by: Steve Rae <srae@broadcom.com>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
[Test HW: Exynos4412 - Trats2]
diff --git a/README b/README
index 4ca04d0..42ece99 100644
--- a/README
+++ b/README
@@ -1773,6 +1773,15 @@
 		regarding the non-volatile storage device. Define this to
 		the eMMC device that fastboot should use to store the image.
 
+		CONFIG_FASTBOOT_GPT_NAME
+		The fastboot "flash" command supports writing the downloaded
+		image to the Protective MBR and the Primary GUID Partition
+		Table. (Additionally, this downloaded image is post-processed
+		to generate and write the Backup GUID Partition Table.)
+		This occurs when the specified "partition name" on the
+		"fastboot flash" command line matches this value.
+		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
+
 - Journaling Flash filesystem support:
 		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
 		CONFIG_JFFS2_NAND_DEV