DSP: Eliminate some non-standard C code

Cleaned out some non-standard C code, typeof() and using
"const" variables as constants.

Also added some initial IAR support.

Signed-off-by: TTornblom <thomas.tornblom@iar.com>

Include/arm_math_types_f16.h

@@ -136,14 +136,23 @@ won't be built.
 
 
 #if defined(ARM_FLOAT16_SUPPORTED)
+
+#if defined(__ICCARM__)
+
+#define F16INFINITY   ((float16_t) INFINITY)
+
+#else
+
+#define F16INFINITY ((float16_t)__builtin_inf())
+
+#endif
+
 #define F16_MAX   ((float16_t)__FLT16_MAX__)
 #define F16_MIN   (-(_Float16)__FLT16_MAX__)
 
 #define F16_ABSMAX   ((float16_t)__FLT16_MAX__)
 #define F16_ABSMIN   ((float16_t)0.0f16)
 
-#define F16INFINITY ((float16_t)__builtin_inf())
-  
 #endif /* ARM_FLOAT16_SUPPORTED*/
 #endif /* !defined( __CC_ARM ) */
 
@@ -152,5 +161,3 @@ won't be built.
 #endif
 
 #endif /* _ARM_MATH_F16_H */
-
-