spi: remove omap 100K driver

The OMAP7xx/OMAP8xx support was removed since all of its boards
have no remaining users. Remove its spi driver as well.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Cc: linux-omap@vger.kernel.org
Cc: Cory Maccarrone <darkstar6262@gmail.com>
Cc: Fabrice Crohas <fcrohas@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>