linux-firmware: add bbappend to modify firmware file names

Upstream changes to the brcmfmac driver require a change to the firmware
file names to match the devid and interface type of the Broadcom chipset.
This also makes it easier for one machine to support multiple chipets in
Yocto.
linux-wandboard(3.10.17): Update SRCREV to 13697f2

The update to the Wandboard Linux kernel includes the following changes:
- wandboard_defconfig: Enable CONFIG_USB_OTG
- wandboard/dts: Fix USB OTG
- wand-rfkill: Change gpio depending on wandboard revision
- wandboard: dts: Add alternate pin support for rev C1
- brcmfmac: Use fw filename and nvram based of devid for sdio.
- wandboard: add revision detect pin to rfkill driver
- wandboard/dts: change EDM gpio to open drain
- wandboard/dts: Enable lcdif in devicetree
- wandboard/dts: add fusion touchscreen to devicetree
- wandboard: Fix bluetooth