Improve configuration of FPGA subsystem

This patch removes the FPGA subsystem configuration through
the CONFIG_FPGA bitmask configuration option.

See README for the new options:

	CONFIG_FPGA,
	CONFIG_FPGA_<vendor>,
	CONFIG_FPGA_<family>

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd-electronics.com>
diff --git a/board/gen860t/fpga.c b/board/gen860t/fpga.c
index 2ba7e0e..3816e52 100644
--- a/board/gen860t/fpga.c
+++ b/board/gen860t/fpga.c
@@ -34,7 +34,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#if (CONFIG_FPGA)
+#if defined(CONFIG_FPGA)
 
 #if 0
 #define GEN860T_FPGA_DEBUG