[MTD] NAND: nandsim page-wise allocation (2/2)

For page wise allocation, an array of flash page pointers is allocated
during initialization. The flash pages are themselves allocated when a
write occurs to the page. The flash pages are deallocated when they
are erased.

Signed-off-by: Vijay Kumar <vijaykumar@bravegnu.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>