Revert "[MTD] Driver for AT26Fxxx dataflash devices"

This reverts commit 340ea370

.

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>