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.

Change-Id: I975dce80ea38033b3282973d760462a1b4bb9caa
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>