Revert "uhd: Set minimum supported version to 3.9.0"

This reverts commit 93ca09ea61.

Ettus Research recommends the use of 3.9 series of UHD releases,
but requiring this version has lead to issues with broken OBS and
packaged binaries by Debian, Ubuntu, and other distributions.

Change-Id: Ie6b175ac6d46d091937380c79fdd0125b16ec75f
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>

Transceiver52M/UHDDevice.cpp

@@ -84,9 +84,15 @@ struct uhd_dev_offset {
 /*
  * USRP version dependent device timings
  */
+#ifdef USE_UHD_3_9
 #define B2XX_TIMING_1SPS	1.7153e-4
 #define B2XX_TIMING_4SPS	1.1696e-4
 #define B2XX_TIMING_4_4SPS	6.18462e-5
+#else
+#define B2XX_TIMING_1SPS	9.9692e-5
+#define B2XX_TIMING_4SPS	6.9248e-5
+#define B2XX_TIMING_4_4SPS	4.52308e-5
+#endif
 
 /*
  * Tx / Rx sample offset values. In a perfect world, there is no group delay

configure.ac

@@ -97,9 +97,12 @@ AS_IF([test "x$with_usrp1" = "xyes"], [
 ])
 
 AS_IF([test "x$with_usrp1" != "xyes"],[
-    PKG_CHECK_MODULES(UHD, uhd >= 003.009)
+    PKG_CHECK_MODULES(UHD, uhd >= 003.009,
+        [AC_DEFINE(USE_UHD_3_9, 1, UHD version 3.9.0 or higher)],
+        [PKG_CHECK_MODULES(UHD, uhd >= 003.005.004)]
+    )
+    AC_DEFINE(USE_UHD, 1, All UHD versions)
     PKG_CHECK_MODULES(FFTWF, fftw3f)
-    AC_DEFINE(USE_UHD, 1, Using UHD driver)
 ])
 
 AS_IF([test "x$with_singledb" = "xyes"], [