serial: sprd: Fix DMA buffer leak issue

Release DMA buffer when _probe() returns failure to avoid memory leak.

Fixes: f4487db5 ("serial: sprd: Add DMA mode support")
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230725064053.235448-2-chunyan.zhang@unisoc.com


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