fix build error: "make" gives error, only "TARGET=X make" builds tinySA4.*

undefined TARGET defines both TINYSA3 and TINYSA4
any value of TARGET builds the F303 version
it is not possible to build the tinySA (TINYSA3) version

Signed-off-by: Martin <Ho-Ro@users.noreply.github.com>

nanovna.h

@@ -18,7 +18,7 @@
  */
 #include "ch.h"
 
-//#ifdef TINYSA_F303
+#ifdef TINYSA_F303
 #ifdef TINYSA_F072
 #error "Remove comment for #ifdef TINYSA_F303"
 #endif
@@ -26,7 +26,7 @@
 #define TINYSA4
 #endif
 #define TINYSA4_PROTO
-//#endif
+#endif
 
 #ifdef TINYSA_F072
 #ifdef TINYSA_F303