lightnvm: implemented L2P TBL transfer command.

This patch represents the first step toward full suspend & resume
of device state across boots by using the L2P command to fetch
the L2P mapping table and reconstruct it in LightNVM.
state of various nvm_block structures et cetera is still pending.

The L2P command to map DMA memory into PRP
lists for transferring a larger (1MB) chunk of table contents per
iteration. Finally the LightNVM core is modified to initialize its
trans & rev_trans maps using the new command.