cxl: Add support to handle user feature commands for set feature

Add helper function to parse the user data from fwctl RPC ioctl and
send the parsed input parameters to cxl_set_feature() call.

Link: https://patch.msgid.link/r/20250307205648.1021626-6-dave.jiang@intel.com


Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>