serial: altera_jtaguart: handle uart_add_one_port() failures

serial: altera_jtaguart: handle uart_add_one_port() failures

altera_jtaguart_probe() maps the register window before registering the
UART port, but it ignores failures from uart_add_one_port(). If port
registration fails, probe still returns success and the mapping remains
live until a later remove path that is not part of probe failure cleanup.

Return the uart_add_one_port() error and unmap the register window on
that failure path.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: 5bcd601049c6 ("serial: Add driver for the Altera JTAG UART")
Cc: stable <stable@kernel.org>
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
Link: https://patch.msgid.link/20260512065837.79528-1-mhun512@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>