scsi: documentation: Fix case of 'scsi_device' struct mention(s)

In scsi_mid_low_api.txt a the scsi_device structure is mentioned
several times, but the leading 's' is uppercase (Scsi_device)
and should be lowercase (scsi_device).  Fixed by this commit.
Signed-off-by: John Pittman <jpittman@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/scsi/scsi_mid_low_api.txt

@@ -319,12 +319,12 @@ struct Scsi_Host:
         instance. If the reference count reaches 0 then the given instance
         is freed
 
-The Scsi_device structure has had reference counting infrastructure added.
-This effectively spreads the ownership of struct Scsi_device instances
+The scsi_device structure has had reference counting infrastructure added.
+This effectively spreads the ownership of struct scsi_device instances
 across the various SCSI layers which use them. Previously such instances
 were exclusively owned by the mid level. See the access functions declared
 towards the end of include/scsi/scsi_device.h . If an LLD wants to keep
-a copy of a pointer to a Scsi_device instance it should use scsi_device_get()
+a copy of a pointer to a scsi_device instance it should use scsi_device_get()
 to bump its reference count. When it is finished with the pointer it can
 use scsi_device_put() to decrement its reference count (and potentially
 delete it).