Add rebrand language referring to the Nexys 4 DDR

Author: artvvb

Nexys-A7-100T-Master.xdc

@@ -2,6 +2,7 @@
 ## To use it in a project:
 ## - uncomment the lines corresponding to used pins
 ## - rename the used ports (in each line, after get_ports) according to the top level signal names in the project
+## Note: As the Nexys 4 DDR was rebranded to the Nexys A7 with no substantial changes, this XDC file will also work for the Nexys 4 DDR.
 
 ## Clock signal
 #set_property -dict { PACKAGE_PIN E3    IOSTANDARD LVCMOS33 } [get_ports { CLK100MHZ }]; #IO_L12P_T1_MRCC_35 Sch=clk100mhz