mmc: card: Adding support for sanitize in eMMC 4.5

The sanitize support is added as a user-app ioctl call, and
was removed from the block-device request, since its purpose is
to be invoked not via File-System but by a user.

This feature deletes the unmap memory region of the eMMC card,
by writing to a specific register in the EXT_CSD.

unmap region is the memory region that was previously deleted
(by erase, trim or discard operation).

In order to avoid timeout when sanitizing large-scale cards,
the timeout for sanitize operation is 240 seconds.

Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Chris Ball <cjb@laptop.org>