RT2400 rfkill support

configname: CONFIG_RT2400PCI_RFKILL

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Wireless LAN
└─>RT2400 rfkill support
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
This adds support for integrated rt2400 devices that feature a
hardware button to control the radio state.
This feature depends on the RF switch subsystem rfkill.