Revert "[MTD] Driver for AT26Fxxx dataflash devices"

This reverts commit 340ea370c2ce89d1c15fbf785460f2f74314ce58.

It's not needed given the other m25p80 patch (which now handles
at26 "dataflash" as well as most other standard SPI flash chips),
and requires a controller driver that won't be merged upstream
(supplanted by drivers/spi/atmel_spi.c) ... the submitter of
that at91_dataflash26.c driver concurred.

Requested by David Brownell <david-b@pacbell.net>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>