docs: ABI: update OCP TimeCard sysfs entries

Update documentation according to the changes in the driver.

New attributes group tty is exposed and ttyGNSS, ttyGNSS2, ttyMAC and
ttyNMEA are moved to this group. Also, these attributes are no more
links to the devices but rather simple text files containing names of
tty devices.

Signed-off-by: Vadim Fedorenko <[e-mail]>
Reviewed-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/ABI/testing/sysfs-timecard

···
 		the estimated point where the FPGA latches the PHC time.  This
 		value may be changed by writing an unsigned integer.
 
-What:		/sys/class/timecard/ocpN/ttyGNSS
-What:		/sys/class/timecard/ocpN/ttyGNSS2
-Date:		September 2021
-Contact:	Jonathan Lemon <[e-mail]>
-Description:	These optional attributes link to the TTY serial ports
-		associated with the GNSS devices.
+What:		/sys/class/timecard/ocpN/tty
+Date:		August 2024
+Contact:	Vadim Fedorenko <[e-mail]>
+Description:	(RO) Directory containing the sysfs nodes for TTY attributes
 
-What:		/sys/class/timecard/ocpN/ttyMAC
-Date:		September 2021
+What:		/sys/class/timecard/ocpN/tty/ttyGNSS
+What:		/sys/class/timecard/ocpN/tty/ttyGNSS2
+Date:		August 2024
 Contact:	Jonathan Lemon <[e-mail]>
-Description:	This optional attribute links to the TTY serial port
-		associated with the Miniature Atomic Clock.
+Description:	(RO) These optional attributes contain names of the TTY serial
+		ports associated with the GNSS devices.
 
-What:		/sys/class/timecard/ocpN/ttyNMEA
-Date:		September 2021
+What:		/sys/class/timecard/ocpN/tty/ttyMAC
+Date:		August 2024
 Contact:	Jonathan Lemon <[e-mail]>
-Description:	This optional attribute links to the TTY serial port
-		which outputs the PHC time in NMEA ZDA format.
+Description:	(RO) This optional attribute contains name of the TTY serial
+		port associated with the Miniature Atomic Clock.
+
+What:		/sys/class/timecard/ocpN/tty/ttyNMEA
+Date:		August 2024
+Contact:	Jonathan Lemon <[e-mail]>
+Description:	(RO) This optional attribute contains name of the TTY serial
+		port which outputs the PHC time in NMEA ZDA format.
 
 What:		/sys/class/timecard/ocpN/utc_tai_offset
 Date:		September 2021