Wunused-variable: Fixed all unused variables in src

This commit addresses all warnings emitted from -Wunused-variable
in the C++ src.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/hm11/hm11.cxx

@@ -82,7 +82,6 @@ bool HM11::dataAvailable(unsigned int millis)
   timeout.tv_sec = 0;
   timeout.tv_usec = millis * 1000;
 
-  int nfds;  
   fd_set readfds;
 
   FD_ZERO(&readfds);