serial: amba-pl011: move variable into CONFIG_DMA_ENGINE conditional

Variable dmacr is only used if DMA is enabled, so move it into the
CONFIG_DMA_ENGINE conditional.

Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240407002709.16224-3-l.sanfilippo@kunbus.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>