Documentation/ABI: Add new sysfs field to sysfs-platform-mellanox-pmc

Document newly added "count_clock" sysfs entry for the Mellanox
BlueField PMC driver.

Signed-off-by: Shravan Kumar Ramani <[e-mail]>
Reviewed-by: David Thompson <[e-mail]>
Link: https://lore.kernel.org/r/3[e-mail]
[ij: corrected KernelVersion & Date]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

Documentation/ABI/testing/sysfs-platform-mellanox-pmc

···
 		Writing 0 to the sysfs will clear the counter, writing any other
 		value is not allowed.
 
+What:		/sys/bus/platform/devices/<HID>/hwmon/hwmonX/<block>/count_clock
+Date:		Mar 2025
+KernelVersion:	6.14
+Contact:	"Shravan Kumar Ramani <[e-mail]>"
+Description:
+		Use a counter for counting cycles. This is used to repurpose/dedicate
+		any of the counters in the block to counting cycles. Each counter is
+		represented by a bit (bit 0 for counter0, bit1 for counter1 and so on)
+		and setting the corresponding bit will reserve that specific counter
+		for counting cycles and override the event<N> setting.