NAND: rearrange ONFI revision checking, add ONFI 2.3

This patch sync with Brian's patch on Linux in nand_flash_detect_onfi()

	commit b7b1a29d94c17e4341856381bccb4d17495bea60
	Author: Brian Norris <computersforpeace@gmail.com>
	Date:   Sun Dec 12 00:23:33 2010 -0800

	    mtd: nand: rearrange ONFI revision checking, add ONFI 2.3

	    In checking for the ONFI revision, the first conditional (for checking
	    "unsupported" ONFI) seems unnecessary.  All ONFI revisions should be
	    backwards-compatible; even if this is not the case on some newer ONFI
	    revision, it should simply fail the second version-checking if-else block
	    (i.e., the bit-fields for 1.0, 2.0, etc. would not be set to 1). Thus, we
	    move our "unsupported" condition after having checked each bit field.

	    Also, it's simple enough to add a condition for ONFI revision 2.3. Note
	    that this does *NOT* mean we handle all new features of ONFI versions
	    above 1.0.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Florian Fainelli <ffainelli@freebox.fr>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

Signed-off-by: Florian Fainelli <florian@openwrt.org>