mtd: nand: don't use read_buf for 8-bit ONFI transfers

mtd: nand: don't use read_buf for 8-bit ONFI transfers

Porting below commit from linux-tree, preserving original authorship & commit log
commit bd9c6e99b58255b9de1982711ac9487c9a2f18be
Author:     Brian Norris <computersforpeace@gmail.com>
mtd: nand: don't use read_buf for 8-bit ONFI transfers

  Use a repeated read_byte() instead of read_buf(), since for x16 buswidth
  devices, we need to avoid the upper I/O[16:9] bits. See the following
  commit for reference:

  commit 05f7835975dad6b3b517f9e23415985e648fb875 (from linux-tree)
  Author: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
  Date:   Thu Dec 5 22:22:04 2013 +0100

      mtd: nand: don't use {read,write}_buf for 8-bit transfers

  Now, I think that all barriers to probing ONFI on x16 devices are
  removed, so remove the check from nand_flash_detect_onfi().

Signed-off-by: Pekon Gupta <pekon@ti.com>