cxl/region: decrement ->nr_targets on error in cxl_region_attach()

The ++ needs a match -- on the clean up path.  If the p->nr_targets
value gets to be more than 16 it leads to uninitialized data in
cxl_port_setup_targets().

drivers/cxl/core/region.c:995 cxl_port_setup_targets() error: uninitialized symbol 'eiw'.

Fixes: 27b3f8d1 ("cxl/region: Program target lists")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YuepCvUAoCtdpcoO@kili


Signed-off-by: Dan Williams <dan.j.williams@intel.com>