radioDevice: GSMRATE macro must have parentheses around its definition.

So we had the following define:
   #define GSMRATE       1625e3/6

Now, I wanted to use it in the following expression:
   3.0/GSMRATE
which turns into:
   3.0/1625e3/6
while what I really wanted is:
   3.0/(1625e3/6) = 3.0/1625e3*6

To avoid this, all macros with calculations must be enclosed in parentheses.

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

Transceiver52M/radioDevice.h

@@ -22,7 +22,7 @@
 #include "config.h"
 #endif
 
-#define GSMRATE       1625e3/6
+#define GSMRATE       (1625e3/6)
 
 /** a 64-bit virtual timestamp for radio data */
 typedef unsigned long long TIMESTAMP;