usb: Fix typo in documentation

simliar -> similar

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

docs/usb-storage.txt

@@ -34,7 +34,7 @@ with tree logical units:
 Number three emulates the classic bulk-only transport protocol too.
 It's called "usb-bot".  It shares most code with "usb-storage", and
 the guest will not be able to see the difference.  The qemu command
-line interface is simliar to usb-uas though, i.e. no automatic scsi
+line interface is similar to usb-uas though, i.e. no automatic scsi
 disk creation.  It also features support for up to 16 LUNs.  The LUN
 numbers must be continuous, i.e. for three devices you must use 0+1+2.
 The 0+1+5 numbering from the "usb-uas" example isn't going to work