ufs: Add Initial Support for UFS subsystem

ufs: Add Initial Support for UFS subsystem

Add Support for UFS Host Controller Interface (UFSHCI) for communicating
with Universal Flash Storage (UFS) devices. The steps to initialize the
host controller interface are the following:

- Initiate the Host Controller Initialization process by writing to the
Host controller enable register.
- Configure the Host Controller base address registers by allocating a
host memory space and related data structures.
- Unipro link startup procedure
- Check for connected device
- Configure UFS host controller to process requests

Also register this host controller as a SCSI host controller.

Taken from Linux Kernel v5.2 (drivers/scsi/ufs/ufshcd.c) and ported to
U-boot.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>