wrt55agv2-spidevs: fix compile issues

i think this breakage was introduced when linux moved to uapi header

Signed-off-by: John Crispin <blogic@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41493 3c298f89-4303-0410-b956-a3cf2f4a3e73