sata_dwc_460ex: fix resource leak on error path

commit 4aaa71873ddb9faf4b0c4826579e2f6d18ff9ab4 upstream.

DMA mapped IO should be unmapped on the error path in probe() and
unconditionally on remove().

Fixes: 62936009f35a ([libata] Add 460EX on-chip SATA driver, sata_dwc_460ex)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>