scsi: ufs: Add DeepSleep feature

DeepSleep is a UFS v3.1 feature that achieves the lowest power consumption
of the device, apart from power off.

In DeepSleep mode, no commands are accepted, and the only way to exit is
using a hardware reset or power cycle.

This patch assumes that if a power cycle was an option, then power off
would be preferable, so only exit via a hardware reset is supported.

Drivers that wish to support DeepSleep need to set a new capability flag
UFSHCD_CAP_DEEPSLEEP and provide a hardware reset via the existing
 ->device_reset() callback.

It is assumed that UFS devices with wspecversion >= 0x310 support
DeepSleep.

[mkp: dropped sysfs ABI doc due to conflicts]

Link: https://lore.kernel.org/r/20201103141403.2142-2-adrian.hunter@intel.com


Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Can Guo <cang@codeaurora.org>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>