mmc: block: handle flush request timeout

In case of a flush request timeout, an error is returned
to the block layer.
The problem with this is that the eMMC card is left in
programming state and while the device is in the
programming state it cannot serve any request.
This commit moves the card out of the programming state,
in case of timeout, by issuing HPI, thereby allowing the
device to continue serving requests.
Some filesystems, such as EXT4, remount the partition as
read-only after receiving an error from the block layer, thus
this change will allow the remounted partition to work as the
card can serve read request thanks to the HPI.

In case where the card doesn't even respond to HPI it
cannot serve any request, thereby, this commit reset the
card in such catastrophic cases.

Change-Id: Idbca6ff3a420a954c61cf4fb79c9094542888d89
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>