configs/common/kernel: refactor and comment

This reorders some options and marks various sections by name.

This also force enables BTRFS.

configs/common/kernel

+# General kernel settings
 CONFIG_KERNEL_AIO=y
 CONFIG_KERNEL_FHANDLE=y
 CONFIG_KERNEL_FANOTIFY=y
@@ -37,14 +38,16 @@ CONFIG_KERNEL_NET_NS=y
 CONFIG_KERNEL_LXC_MISC=y
 CONFIG_KERNEL_DEVPTS_MULTIPLE_INSTANCES=y
 CONFIG_KERNEL_POSIX_MQUEUE=y
-CONFIG_KERNEL_USB_UHCI_PLATFORM=y
-CONFIG_KERNEL_USB_UHCI_HCD=y
 CONFIG_KERNEL_MTD_SPI_NOR_USE_4K_SECTORS_LIMIT=4092
+
+# File-systems
+CONFIG_KERNEL_BTRFS_FS=y
+CONFIG_KERNEL_BTRFS_FS_POSIX_ACL=y
 CONFIG_KERNEL_NFS_FS=y
 CONFIG_KERNEL_NFS_V2=y
 CONFIG_KERNEL_NFS_V3=y
 CONFIG_KERNEL_ROOT_NFS=y
-
+# File-sustem modules
 CONFIG_PACKAGE_kmod-fs-btrfs=y
 CONFIG_PACKAGE_kmod-fs-ext4=y
 CONFIG_PACKAGE_kmod-fs-vfat=y
@@ -55,19 +58,28 @@ CONFIG_PACKAGE_kmod-nls-cp437=y
 CONFIG_PACKAGE_kmod-nls-iso8859-1=y
 CONFIG_PACKAGE_kmod-nls-utf8=y
 
-CONFIG_DEFAULT_kmod-usb-core=y
-CONFIG_DEFAULT_kmod-usb-storage=y
-CONFIG_DEFAULT_kmod-usb2=y
-CONFIG_DEFAULT_kmod-usb2-fsl=y
-CONFIG_DEFAULT_kmod-usb3=y
+# Ethernet
 CONFIG_DEFAULT_ip6tables=y
 CONFIG_DEFAULT_iptables=y
 
-CONFIG_PACKAGE_kmod-veth=y
-CONFIG_PACKAGE_kmod-vxlan=y
+# Wi-Fi
+CONFIG_PACKAGE_kmod-ath=y
+CONFIG_ATH_USER_REGD=y
+CONFIG_PACKAGE_ATH_DFS=y
+CONFIG_PACKAGE_kmod-ath9k=y
+CONFIG_PACKAGE_kmod-ath9k-common=y
+CONFIG_PACKAGE_kmod-cfg80211=y
 
-CONFIG_PACKAGE_kmod-sound-core=y
+# Firewall
+CONFIG_DEFAULT_ip6tables=y
+CONFIG_DEFAULT_iptables=y
 
+# USB
+CONFIG_DEFAULT_kmod-usb-core=y
+CONFIG_DEFAULT_kmod-usb-storage=y
+CONFIG_DEFAULT_kmod-usb2=y
+CONFIG_DEFAULT_kmod-usb2-fsl=y
+CONFIG_DEFAULT_kmod-usb3=y
 CONFIG_PACKAGE_kmod-usb-core=y
 CONFIG_PACKAGE_kmod-usb-ehci=y
 CONFIG_PACKAGE_kmod-usb-hid=y
@@ -77,13 +89,7 @@ CONFIG_PACKAGE_kmod-usb-uhci=y
 CONFIG_PACKAGE_kmod-usb2=y
 CONFIG_PACKAGE_kmod-usb3=y
 
-CONFIG_PACKAGE_kmod-ath=y
-CONFIG_ATH_USER_REGD=y
-CONFIG_PACKAGE_ATH_DFS=y
-CONFIG_PACKAGE_kmod-ath9k=y
-CONFIG_PACKAGE_kmod-ath9k-common=y
-CONFIG_PACKAGE_kmod-cfg80211=y
-
+# Watchdog
 CONFIG_KERNEL_WATCHDOG_PRETIMEOUT_GOV=y
 CONFIG_KERNEL_WATCHDOG_PRETIMEOUT_GOV_NOOP=n
 CONFIG_KERNEL_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOOP=n
@@ -95,3 +101,6 @@ CONFIG_KERNEL_WATCHDOG_NOWAYOUT=y
 # HaaS
 CONFIG_KERNEL_FAIR_GROUP_SCHED=y
 CONFIG_KERNEL_CFS_BANDWIDTH=y
+
+# Sound
+CONFIG_PACKAGE_kmod-sound-core=y