debian: Require fftw3 header files for osmo-trx

Install missing development package to get osmo-trx to build.

Change-Id: Id80937724d5e4da4ed555cbabfcd3e2457cb2a19
diff --git a/debian/control b/debian/control
index 0aef88e..b8ec911 100644
--- a/debian/control
+++ b/debian/control
@@ -3,7 +3,7 @@
 Section: net
 Priority: optional
 Standards-Version: 3.9.3
-Build-Depends: debhelper (>= 9), autotools-dev, libdbd-sqlite3, pkg-config, dh-autoreconf, libuhd-dev, libusb-1.0-0-dev, libboost-all-dev, hardening-wrapper
+Build-Depends: debhelper (>= 9), autotools-dev, libdbd-sqlite3, pkg-config, dh-autoreconf, libuhd-dev, libusb-1.0-0-dev, libboost-all-dev, hardening-wrapper, libfftw3-dev
 Homepage: http://openbsc.osmocom.org/trac/wiki/OsmoTRX
 Vcs-Git: git://git.osmocom.org/osmo-trx
 Vcs-Browser: http://cgit.osmocom.org/osmo-trx