hw/ufs: Initial commit for emulated Universal-Flash-Storage

Universal Flash Storage (UFS) is a high-performance mass storage device
with a serial interface. It is primarily used as a high-performance
data storage device for embedded applications.

This commit contains code for UFS device to be recognized
as a UFS PCI device.
Patches to handle UFS logical unit and Transfer Request will follow.

Signed-off-by: Jeuk Kim <jeuk20.kim@samsung.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 10232660d462ee5cd10cf673f1a9a1205fc8276c.1693980783.git.jeuk20.kim@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>