mtd: nand: use more reasonable integer types

Use 'unsigned int' instead of 'unsigned long' in the NAND chip description data
structure, because 32-bits is more than enough for our purposes. We do not need
64-bits, which is what we end up on 64-bit architectures. We declare many
instances of this data structure, so this should help saving some amount of
memory.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>