mtd/NAND: Add FSMC driver support

mtd/NAND: Add FSMC driver support

Flexible static memory controller is a peripheral provided by ST,
which controls the access to NAND chips along with many other
memory device chips eg NOR, SRAM.

This patch adds the driver support for FSMC controller interfacing
with NAND memory.

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>
Acked-by: Scott Wood <scottwood@freescale.com>