Fix some compiler warnings in fpga code

Signed-off-by: Steffen Vogel <post@steffenvogel.de>

fpga/include/villas/fpga/ips/rtds.hpp

@@ -52,3 +52,9 @@ private:
 } // namespace ip
 } // namespace fpga
 } // namespace villas
+
+#ifndef FMT_LEGACY_OSTREAM_FORMATTER
+template <>
+class fmt::formatter<villas::fpga::ip::RtdsGtfpga>
+    : public fmt::ostream_formatter {};
+#endif

fpga/tests/unit/dma.c

@@ -17,8 +17,6 @@ int main(int argc, char *argv[])
 	villasfpga_handle vh;
 	villasfpga_memory mem1, mem2;
 	void *mem1ptr, *mem2ptr;
-	char line[1024];
-	float f;
 	size_t size;
 
 	if (argv == NULL) {