serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

serial: amba-pl011: get rid of useless wrapper pl011_get_rs485_mode()

Due to earlier code changes function pl011_get_rs485_mode() is now merely
a wrapper for uart_get_rs485_mode() which does not add any further
functionality. So remove it and instead call uart_get_rs485_mode()
directly.

Reviewed-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240407002709.16224-2-l.sanfilippo@kunbus.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>