fpga: tools: Add support for .sdc in Vivado

viv_utils.tcl will now read files with the .sdc suffix using the
read_xdc Vivado command. This is especially useful when I/O timing
constraints in the FPGA and CPLD need to depend on a common constant.


Original-commit: b47b1a467ee5796dbce359ff34c9d55a6acebc82

tools/scripts/viv_utils.tcl

@@ -70,6 +70,9 @@ proc ::vivado_utils::initialize_project { {save_to_disk 0} } {
         } elseif [expr [lsearch {.xdc} $src_ext] >= 0] {
             puts "BUILDER: Adding XDC     : $src_file"
             read_xdc $src_file
+        } elseif [expr [lsearch {.sdc} $src_ext] >= 0] {
+            puts "BUILDER: Adding SDC     : $src_file"
+            read_xdc $src_file
         } elseif [expr [lsearch {.xci} $src_ext] >= 0] {
             puts "BUILDER: Adding IP      : $src_file"
             read_ip $src_file