FROMLIST: scsi: ufs: Limit the number of inflight rb

in host control mode the host is the originator of map requests. To not
flood the device with map requests, use a simple throttling mechanism
that limits the number of inflight map requests.

Bug: 183467926
Bug: 170940265
Bug: 183454255

Link: https://lore.kernel.org/lkml/20210607061401.58884-10-avri.altman@wdc.com/


Signed-off-by: Avri Altman <avri.altman@wdc.com>
Change-Id: I75a5ced3be60569adcd75befa17d8a6340c147fd