greybus: Documentation/sysfs: replace Ara references

Refer to the MDK as GMP MDK.

Signed-off-by: Johan Hovold <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/greybus/Documentation/sysfs-bus-greybus

···
 Description:
 		The AP interface ID, a 1-byte non-zero integer which
 		defines the position of the AP module on the frame.
-		The interface positions are defined in the ARA
+		The interface positions are defined in the GMP
 		Module Developer Kit.
 
 What:		/sys/bus/greybus/devices/N-svc/endo_id
···
 Description:
 		The Endo ID, which is a 2-byte hexadecimal value
 		defined by the Endo layout scheme, documented in
-		the ARA Module Developer Kit.
+		the GMP Module Developer Kit.
 
 What:		/sys/bus/greybus/devices/N-svc/intf_eject
 Date:		October 2015