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/common/spartan2.c b/common/spartan2.c
index 06550b9..457009f 100644
--- a/common/spartan2.c
+++ b/common/spartan2.c
@@ -25,7 +25,7 @@
 #include <common.h>		/* core U-Boot definitions */
 #include <spartan2.h>		/* Spartan-II device family */
 
-#if (CONFIG_FPGA & (CFG_XILINX | CFG_SPARTAN2))
+#if defined(CONFIG_FPGA) && defined(CONFIG_FPGA_SPARTAN2)
 
 /* Define FPGA_DEBUG to get debug printf's */
 #ifdef	FPGA_DEBUG