cxl/hdm: Debug, use decoder name function

cxl/hdm: Debug, use decoder name function

The decoder enum has a name conversion function defined now.

Use that instead of open coding.

Suggested-by: Navneet Singh <navneet.singh@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20230604-dcd-type2-upstream-v2-1-f740c47e7916@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>