[PATCH] Add Linux SPI support

[Sven Schnelle]

Hi List,

this patch adds support for the Linux SPI subsystem. See 
http://www.kernel.org/doc/Documentation/spi/spidev for a 
short introduction.

Usage is as follows:

flashrom -p linux_spi:dev=/dev/spidevX.Y

where X is the bus number, and Y device. It accepts an optional
parameter 'speed' which allows to set the SPI CLK speed in KHz.

I'm using a AVR32 Board
(http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4102) to
program my ThinkPad X60, but it should work on every Linux system.

Signed-off-by: Sven Schnelle