mmc: omap_hsmmc: Kill off cover detection

Cover detection appears to be a feature protecting the SD
card on mobile phones with a slide-cover, such as some Nokia
phones. The idea seems to be to not allow access to the
SD card when the cover is open.

It is only usable with platform data from board files, but
no board file in the kernel is using it, yet it takes up
a sizeable chunk of code in the OMAP HSMMC driver.

Since we do not add new board files for the OMAPs any target
that need this should anyway reimplement it properly using
the device tree, so delete this legacy code.

The driver is marked as orphan in MAINTAINERS by the way.

Cc: Tony Lindgren <tony@atomide.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>