Fix build without fpga support

(cherry picked from commit ae92a6fb35809bda2fefba94005cd267f862a976)

src/drivers/max/driver_fpga.h

@@ -38,7 +38,11 @@ extern struct _starpu_node_ops _starpu_driver_fpga_node_ops;
 
 int fpgaSetDevice(unsigned devid);
 void _starpu_init_fpga(void);
+#ifdef STARPU_USE_FPGA
 void _starpu_fpga_discover_devices (struct _starpu_machine_config *config);
+#else
+#define _starpu_fpga_discover_devices(config) ((void) config)
+#endif
 unsigned _starpu_fpga_get_device_count(void);
 
 uintptr_t _starpu_fpga_allocate_memory(unsigned dst_node, size_t size, int flags);

tests/Makefile.am

@@ -378,6 +378,12 @@ myPROGRAMS +=				\
 endif
 endif
 
+if STARPU_USE_FPGA
+myPROGRAMS +=					\
+	perfmodels/max_fpga			\
+	perfmodels/max_riffa
+endif
+
 MICROBENCHS = \
 	microbenchs/parallel_independent_homogeneous_tasks      \
 	microbenchs/parallel_independent_heterogeneous_tasks    \