SPL: Add YMODEM over UART load support

Adds support for loading U-Boot from UART using YMODEM protocol.
If YMODEM support is enabled in SPL and the romcode indicates
that SPL loaded via UART then SPL will wait for start of a
YMODEM transfer via the console port.

Signed-off-by: Matt Porter <mporter@ti.com>
Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/lib/Makefile b/lib/Makefile
index e6e6ec6..4b5734a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -55,6 +55,9 @@
 COBJS-$(CONFIG_SPL_SPI_FLASH_SUPPORT) += display_options.o
 endif
 
+ifdef CONFIG_SPL_BUILD
+COBJS-$(CONFIG_SPL_YMODEM_SUPPORT) += crc16.o
+endif
 COBJS-y += ctype.o
 COBJS-y += div64.o
 COBJS-y += string.o