Convert CONFIG_CMD_BAT to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_BAT

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/omap4_sdp4430_defconfig b/configs/omap4_sdp4430_defconfig
index 727a450..7229142 100644
--- a/configs/omap4_sdp4430_defconfig
+++ b/configs/omap4_sdp4430_defconfig
@@ -4,6 +4,7 @@
 CONFIG_ARCH_OMAP2PLUS=y
 CONFIG_OMAP44XX=y
 CONFIG_TARGET_OMAP4_SDP4430=y
+CONFIG_CMD_BAT=y
 # CONFIG_SPL_NAND_SUPPORT is not set
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y