cxl: Cleanup partition size and perf helpers

cxl: Cleanup partition size and perf helpers

Now that the 'struct cxl_dpa_partition' array contains both size and
performance information, all paths that iterate over that information
can use a loop rather than hard-code 'ram' and 'pmem' lookups.

Remove, or reduce the scope of the temporary helpers that bridged the
pre-'struct cxl_dpa_partition' state of the code to the post-'struct
cxl_dpa_partition' state.

- to_{ram,pmem}_perf(): scope reduced to just sysfs_emit + is_visible()
  helpers

- to_{ram,pmem}_res(): fold into their only users cxl_{ram,pmem}_size()

- cxl_ram_size(): scope reduced to ram_size_show() (Note,
  cxl_pmem_size() also used to gate nvdimm registration)

In short, memdev sysfs ABI already made the promise that 0-sized
partitions will show for memdevs, but that can be avoided for future
partitions by using dynamic sysfs group visibility (new relative to when
the partition ABI first shipped upstream).

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Alejandro Lucero <alucerop@amd.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Alejandro Lucero <alucerop@amd.com>
Link: https://patch.msgid.link/173864307519.668823.10800104022426067621.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>