Parameters in mic_array_conf.h only get set if not already defined

This allows the user to specify lib_mic_array parameters in xua_conf.h,
overriding the defaults present in the mic_array_conf.h file included in
lib_xua.

For example, the application may use lib_mic_array independent of lib_xua.
This makes that possible.

lib_xua/src/core/pdm_mics/mic_array_conf.h

@@ -3,7 +3,12 @@
 
 #include "xua_conf_full.h"
 
+#ifndef MIC_ARRAY_MAX_FRAME_SIZE_LOG2
 #define MIC_ARRAY_MAX_FRAME_SIZE_LOG2 0
+#endif
+
+#ifndef MIC_ARRAY_NUM_MICS
 #define MIC_ARRAY_NUM_MICS (NUM_PDM_MICS)
+#endif
 
 #endif /* MIC_ARRAY_CONF_H_ */