mtd: add data structures for Extended Parameter Page

Since the ONFI 2.1, the onfi spec adds the Extended Parameter Page
to store the ECC info.

The onfi spec tells us that if the nand chip's recommended ECC codeword
size is not 512 bytes, then the @ecc_bits is 0xff. The host _SHOULD_ then
read the Extended ECC information that is part of the extended parameter
page to retrieve the ECC requirements for this device.

This patch adds
    [1] the neccessary fields for nand_onfi_params{},
    [2] and adds the onfi_ext_ecc_info{} for Extended ECC information,
    [3] adds onfi_ext_section{} for extended sections,
    [4] and adds onfi_ext_param_page{} for the Extended Parameter Page.

Acked-by: Pekon Gupta <pekon@ti.com>
Signed-off-by: Huang Shijie <b32955@freescale.com>
Reviewed-and-tested-by: Brian Norris <computersforpeace@gmail.com>
[Brian: amended for checkpatch.pl]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>