drivers:misc: ti-st: wait for completion at fail

When the line discipline install fails for reasons such as missing user-space
UIM or broken communication between UIM and ST driver, then the ST
attempts/retries to request for ldisc installation again.

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>