This patch adds TopBottom detection for most Macronix chips with CFI V1.0.

The main purpose of this patch is to add detection of the MX29LV400C B
used on the LaCie Ethernet Disk mini V2 NAS.

It detects the following parts correctly:-
MX28F640C3B T
MX29LV002C  B
MX29LV002NC B
MX29LV004C  T
MX29LV400C  T/B
MX29LV800C  T/B
MX29LV160C  T/B
MX29SL800C  T/B
MX29SL802C  T/B

It detects the following uniform part as bottom but it should work
correctly:-
MX29LV040C

For T parts it causes the erase block table to be reversed correctly.
For other parts it avoids the bogus "Assuming top" message.

It does not detect the following correctly:-
MX28F640C3B B
MX29LV002C  T
MX29LV002NC T
MX29LV004C  B
MX29SL400C  T/B
MX29SL402C  T/B

If desired I could supply a more complicated patch to handle these as
well.

Only the MX29LV400C B has been physically tested; others were checked
against their data sheets.
Signed-off-by: Christopher Moore <moore@free.fr>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>