cxl: Enumerate feature commands

cxl: Enumerate feature commands

Add feature commands enumeration code in order to detect and enumerate
the 3 feature related commands "get supported features", "get feature",
and "set feature". The enumeration will help determine whether the driver
can issue any of the 3 commands to the device.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Shiju Jose <shiju.jose@huawei.com>
Link: https://patch.msgid.link/20250220194438.2281088-2-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>