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/include/configs/spear-common.h b/include/configs/spear-common.h
index 8d0f036..75cc5ff 100644
--- a/include/configs/spear-common.h
+++ b/include/configs/spear-common.h
@@ -55,10 +55,10 @@
 #if defined(CONFIG_FLASH_PNOR)
 #define CONFIG_SPEAR_EMI			1
 #else
-#define CONFIG_SPEARSMI				1
+#define CONFIG_ST_SMI
 #endif
 
-#if defined(CONFIG_SPEARSMI)
+#if defined(CONFIG_ST_SMI)
 
 #define CONFIG_SYS_MAX_FLASH_BANKS		2
 #define CONFIG_SYS_FLASH_BASE			(0xF8000000)
@@ -125,7 +125,7 @@
  * U-Boot Environment placing definitions.
  */
 #if defined(CONFIG_ENV_IS_IN_FLASH)
-#ifdef CONFIG_SPEARSMI
+#ifdef CONFIG_ST_SMI
 /*
  * Environment is in serial NOR flash
  */