serial: 8250_dw: Deduplicate LCR checks

All callers of dw8250_check_lcr() perform the same check.
Deduplicate it by moving them into respective call.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240412173931.187411-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>