mtd: nand/fsmc: Modify fsmc driver to accept nand timing parameters via platform

FSMC controllers provide registers to program the required timing values for
attached NAND device. The timing values used until now are relaxed and should
work for all devices.

Although, for read/write performance improvements, the fsmc nand driver should
accept nand timings as a platform data and program the timing parameters into
fsmc registers accordingly.

This patch implements this modification. Additionally, it programs the default
timing parameters if these are not passed via platform data.

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>