tty: hvc: use correct dma alignment size

Use L1_CACHE_BYTES as the dma alignment size, use 'sizeof(long)' as
dma alignment is wrong.

Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
Signed-off-by: Shile Zhang <shile.zhang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20211015024658.1353987-2-xianting.tian@linux.alibaba.com


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