Convert CONFIG_CMD_BMODE to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_BMODE

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Make this default y and depend on mx5/6/7]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/m53evk_defconfig b/configs/m53evk_defconfig
index 74b1ae6..21a29aa 100644
--- a/configs/m53evk_defconfig
+++ b/configs/m53evk_defconfig
@@ -6,6 +6,7 @@
 CONFIG_TARGET_M53EVK=y
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL_NAND_SUPPORT=y
+# CONFIG_CMD_BMODE is not set
 CONFIG_VIDEO=y
 CONFIG_FIT=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/aries/m53evk/imximage.cfg"