[flashrom] Added support for Macronix MX23L1654, MX23L6454, and MX23L12854

[Michael Coppola]

Hi,

I've added support for the Macronix MX23L1654, MX23L6454, and MX23L12854
SPI mask ROM chips.  I do not physically have these chips and have not
tested, but I used the template for the MX23L3254 which I have
previously verified to work with a real chip.

Datasheets:
http://www.mxic.com.tw/Lists/DataSheet/Attachments/1216/MX23L1654,%203.0-3.3...
http://www.mxic.com.tw/Lists/DataSheet/Attachments/1234/MX23L6454,%203.0-3.3...
http://www.mxic.com.tw/Lists/DataSheet/Attachments/1232/MX23L12854,%203.0-3....

Signed-off-by: Michael Coppola