fpga: Guard the LOADMK functionality with CMD_FPGA_LOADMK

Guard the LOADMK functionality with config to provide
an option to enable or disable it.
Enable it for all platforms in mainline which enable CONFIG_CMD_FPGA.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/include/configs/x600.h b/include/configs/x600.h
index 7405419..eae85d6 100644
--- a/include/configs/x600.h
+++ b/include/configs/x600.h
@@ -107,6 +107,7 @@
 #define CONFIG_CMD_DHCP
 #define CONFIG_CMD_ENV
 #define CONFIG_CMD_FPGA
+#define CONFIG_CMD_FPGA_LOADMK
 #define CONFIG_CMD_GPIO
 #define CONFIG_CMD_I2C
 #define CONFIG_CMD_MEMORY