serial: cpm_uart: Fix build error without CONFIG_SERIAL_CPM_CONSOLE

serial: cpm_uart: Fix build error without CONFIG_SERIAL_CPM_CONSOLE

drivers/tty/serial/cpm_uart/cpm_uart_core.c: In function ‘cpm_uart_init_port’:
drivers/tty/serial/cpm_uart/cpm_uart_core.c:1251:7: error: ‘udbg_port’ undeclared (first use in this function); did you mean ‘uart_port’?
  if (!udbg_port)
       ^~~~~~~~~
       uart_port

commit 26b32acafcd2 leave this corner, wrap it with #ifdef block

Fixes: 26b32acafcd2 ("serial: cpm_uart: Protect udbg definitions by CONFIG_SERIAL_CPM_CONSOLE")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20220518135452.39480-1-yuehaibing@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>