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/gen860t.c b/board/gen860t/gen860t.c
index d448f9f..73cc16d 100644
--- a/board/gen860t/gen860t.c
+++ b/board/gen860t/gen860t.c
@@ -254,7 +254,7 @@
 	mii_init ();
 #endif
 
-#if (CONFIG_FPGA)
+#if defined(CONFIG_FPGA)
 	gen860t_init_fpga ();
 #endif
 	return 0;