serial: mvebu-uart: remove unused member nb from struct mvebu_uart

Member nb in struct mvebu_uart is not set nor read. So remove it completely.

Signed-off-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20210624224909.6350-7-pali@kernel.org


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