cxl: Fix a typo in ABI documentation

Fix the attribute name of the configuration record class ID.

Signed-off-by: Philippe Bergheaud <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

Documentation/ABI/testing/sysfs-class-cxl

···
 		Hexadecimal value of the device ID found in this AFU
 		configuration record.
 
-What:           /sys/class/cxl/<afu>/cr<config num>/vendor
+What:           /sys/class/cxl/<afu>/cr<config num>/class
 Date:           February 2015
 Contact:        [e-mail]
 Description:    read only