refactor(tc): introduce a new file tc-fpga.dtsi

A Total Compute platform supports FVP and FPGA target. And it's possible
that these two targets have different hardware components. For this
reason, this patch introduces a new file tc-fpga.dtsi for FPGA related
DT binding.

As a result, this patch moves out FVP and FPGA specific macros into
tc-fvp.dtsi and tc-fpga.dtsi respectively.

Change-Id: I48d7d30d0c500cec5500f1a2a680e8b3a276ea99
Signed-off-by: Leo Yan <leo.yan@arm.com>
diff --git a/fdts/tc3.dts b/fdts/tc3.dts
index 5522210..52b0856 100644
--- a/fdts/tc3.dts
+++ b/fdts/tc3.dts
@@ -31,6 +31,8 @@
 #include "tc-common.dtsi"
 #if TARGET_FLAVOUR_FVP
 #include "tc-fvp.dtsi"
+#else
+#include "tc-fpga.dtsi"
 #endif /* TARGET_FLAVOUR_FVP */
 #include "tc-base.dtsi"