cxl/Documentation: Add more description about min/max scrub cycle

user can configurare scrub cycle for a region or a memory device via
sysfs interface. Currently, these interfaces have not enough description
for the return value. So adding return value description to these
interfaces.

Suggested-by: Alison Schofield <[e-mail]>
Signed-off-by: Shiju Jose <[e-mail]>
Signed-off-by: Li Ming <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Reviewed-by: Dave Jiang <[e-mail]>
Reviewed-by: Davidlohr Bueso <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Dave Jiang <[e-mail]>

Documentation/ABI/testing/sysfs-edac-scrub

···
 		(RO) Supported minimum scrub cycle duration in seconds
 		by the memory scrubber.
 
+		Device-based scrub: returns the minimum scrub cycle
+		supported by the memory device.
+
+		Region-based scrub: returns the max of minimum scrub cycles
+		supported by individual memory devices that back the region.
+
 What:		/sys/bus/edac/devices/<dev-name>/scrubX/max_cycle_duration
 Date:		March 2025
 KernelVersion:	6.15
···
 Description:
 		(RO) Supported maximum scrub cycle duration in seconds
 		by the memory scrubber.
+
+		Device-based scrub: returns the maximum scrub cycle supported
+		by the memory device.
+
+		Region-based scrub: returns the min of maximum scrub cycles
+		supported by individual memory devices that back the region.
+
+		If the memory device does not provide maximum scrub cycle
+		information, return the maximum supported value of the scrub
+		cycle field.
 
 What:		/sys/bus/edac/devices/<dev-name>/scrubX/current_cycle_duration
 Date:		March 2025