cxl/region: Drop goto pattern in cxl_dax_region_alloc()

cxl/region: Drop goto pattern in cxl_dax_region_alloc()

In cxl_dax_region_alloc(), there is a goto pattern to release the rwsem
cxl_region_rwsem when the function returns, the down_read() and up_read
can be replaced by a guard(rwsem_read) then the goto pattern can be
removed.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Li Ming <ming.li@zohomail.com>
Link: https://patch.msgid.link/20250221012453.126366-7-ming.li@zohomail.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>