SPL: Move the omap SPL framework to common/spl

Add a new flag, CONFIG_SPL_FRAMEWORK to opt into the common/spl SPL
framework, enable on all of the previously using boards.  We move the
spl_ymodem.c portion to common/ and spl_mmc.c to drivers/mmc/.  We leave
the NAND one in-place as we plan to replace it later in this series.

We use common/spl to avoid linker problems with respect to merging
constant strings in objects.   Otherwise all strings in common/ will be
linked in and kept which grows SPL in size too much.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/drivers/mmc/Makefile b/drivers/mmc/Makefile
index 2b96cdc..941a909 100644
--- a/drivers/mmc/Makefile
+++ b/drivers/mmc/Makefile
@@ -25,8 +25,11 @@
 
 LIB	:= $(obj)libmmc.o
 
-ifdef CONFIG_SPL_MMC_LOAD
+ifdef CONFIG_SPL_BUILD
 COBJS-$(CONFIG_SPL_MMC_LOAD)	+= spl_mmc_load.o
+ifdef CONFIG_SPL_FRAMEWORK
+COBJS-$(CONFIG_SPL_MMC_SUPPORT) += spl_mmc.o
+endif
 endif
 
 COBJS-$(CONFIG_BFIN_SDH) += bfin_sdh.o