Convert CONFIG_CMD_FPGA_LOADBP et al to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_FPGA_LOADBP
   CONFIG_CMD_FPGA_LOADFS
   CONFIG_CMD_FPGA_LOADMK
   CONFIG_CMD_FPGA_LOADP

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/x600_defconfig b/configs/x600_defconfig
index 3aaba16..2e5d5f1 100644
--- a/configs/x600_defconfig
+++ b/configs/x600_defconfig
@@ -20,6 +20,7 @@
 CONFIG_LOOPW=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_USB=y
+CONFIG_CMD_FPGA_LOADMK=y
 CONFIG_CMD_GPIO=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y