tty: serial: Fix refcount leak bug in ucc_uart.c

tty: serial: Fix refcount leak bug in ucc_uart.c

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v4.19.256 by commit 59bc4c19d53bdac61ec952c01c6e864f5f0f8367. For more details please see the references link.