USB: android: Ensure at least two serial ports are initialized

Driver allows serial ports and transports initialization only once
during bootup. Hence, any attempt by user to switch to a composition
having more number of serial ports fails. As compositions with two
serial ports (with second one using TTY) are pretty common, make
sure there are at least two serials ports initialized to allow this.
And mark 2nd port to use TTY if user didn't specify the transport
explicitly.

CRs-fixed: 1012067
Change-Id: Ic1fe0044e2a54ab3243ae1f151c063d91de422d5
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>