dsp5680xx: fix compilation problems

use a more specific global variable name than "context", which
can easily conflict with other things.

src/target/dsp5680xx.h

@@ -217,7 +217,9 @@ struct dsp5680xx_common{
   //TODO
   uint32_t stored_pc;
   int flush;
-}context;
+};
+
+extern struct dsp5680xx_common dsp5680xx_context;
 
 static inline struct dsp5680xx_common *target_to_dsp5680xx(struct target *target){
   return target->arch_info;