Automatic software update from TFTP server

The auto-update feature allows to automatically download software updates
from a TFTP server and store them in Flash memory during boot. Updates are
contained in a FIT file and protected with SHA-1 checksum.

More detailed description can be found in doc/README.update.

Signed-off-by: Rafal Czubak <rcz@semihalf.com>
Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>

common/Makefile

diff --git a/common/Makefile b/common/Makefile
index 8bddf8e..f00cbd9 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -153,6 +153,7 @@
 COBJS-y += kgdb.o
 COBJS-$(CONFIG_LCD) += lcd.o
 COBJS-$(CONFIG_LYNXKDI) += lynxkdi.o
+COBJS-$(CONFIG_UPDATE_TFTP) += update.o
 COBJS-$(CONFIG_USB_KEYBOARD) += usb_kbd.o
 COBJS-$(CONFIG_DDR_SPD) += ddr_spd.o