Enable hwmon and sensor drivers

hwmon core, nct7904, lm75, and at24.
diff --git a/meta-ast2400/recipes-kernel/linux/linux-obmc_%.bbappend b/meta-ast2400/recipes-kernel/linux/linux-obmc_%.bbappend
index 6d7ae27..0575ac1 100644
--- a/meta-ast2400/recipes-kernel/linux/linux-obmc_%.bbappend
+++ b/meta-ast2400/recipes-kernel/linux/linux-obmc_%.bbappend
@@ -1,2 +1,2 @@
 FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
-SRC_URI += "file://defconfig"
+SRC_URI += "file://defconfig hwmon.cfg"