st_smi: Add support for SPEAr SMI driver

SMI is the serial memory interface controller provided by ST.

Earlier, a driver exists in the u-boot source code for the SMI IP. However, it
was specific to spear platforms. This commit converts the same driver to a more
generic driver. As a result, the driver files are renamed to st_smi.c and
st_smi.h and moved into drivers/mtd folder for reusability by other platforms
using smi controller peripheral.

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Amit Virdi <amit.virdi@st.com>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 5a5ecdf..543c845 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -35,7 +35,7 @@
 COBJS-$(CONFIG_FTSMC020) += ftsmc020.o
 COBJS-$(CONFIG_FLASH_CFI_LEGACY) += jedec_flash.o
 COBJS-$(CONFIG_MW_EEPROM) += mw_eeprom.o
-COBJS-$(CONFIG_SPEARSMI) += spr_smi.o
+COBJS-$(CONFIG_ST_SMI) += st_smi.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)