mtd: nand: pxa3xx: add raw read support

mtd: nand: pxa3xx: add raw read support

Raw read support is added by editing a few code sections:

    ->handle_data_pio() includes the ECC bytes that are not consumed
    anymore by the ECC engine.

    ->prepare_set_command() is changed so that the ECC bytes are
    requested as part of the data I/O length.

    ->drain_fifo() shall also avoid checking the R/B pin too often
    when in raw mode.

    ->read_page_raw()/->read_oob_raw() are written from scratch.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Jagan Teki <jagan@openedev.com>