package/gr-osmosdr: fix dependencies

package/gr-osmosdr: fix dependencies

gr-osmosdr fails with:
CMake Error at /somewhere/buildroot/output/host/mipsel-buildroot-linux-gnu/sysroot/usr/lib/cmake/gnuradio/GnuradioConfig.cmake:116 (include):
  include could not find load file:

    /somewhere/buildroot/output/host/mipsel-buildroot-linux-gnu/sysroot/usr/lib/cmake/gnuradio/gnuradio-filterConfig.cmake
Call Stack (most recent call first):
  CMakeLists.txt:45 (find_package)

gr-osmosdr depends on BR2_PACKAGE_GNURADIO_BLOCKS, BR2_PACKAGE_GNURADIO_FFT and
BR2_PACKAGE_GNURADIO_FILTER.

fix:
- http://autobuild.buildroot.net/results/1781db2b8c28641167f7a39a4d799930db13f9bf/

Signed-off-by: Gwenhael Goavec-Merou <gwenhael.goavec-merou@trabucayre.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>