c400eef3772b7dc470eefae02a1288c2b125e25c introduced some defines to handle
older kernel headers. However, the check is done before the corresponding
kernel header (dvb/frontend.h) is included. As a result the macros are
always defined with results in 'redefined' errors with newer kernel
headers.
Move the check after the include to fix this.
https://bugzilla.gnome.org/show_bug.cgi?id=730570