Introduce HW_SAMPR_MIN_GE_22 macro

Gives us the lowest HW sample rate that's >= 22KHz.

Needed because some targets that don't support 22K support 11K or 8K, so
HW_SAMPR_MIN will give us much lower quality than is acceptable.

Take advantage of this new macro in the SDL, MIDI, and MIKMOD plugins,
and implement a crude "fast enough" test to enable higher sample rates
on more capable targets.

Change-Id: I6ad38026fb3410c62da028e78512e027729bb851

apps/plugins/mikmod/mikmod_supp.h

@@ -63,8 +63,29 @@ int mmsupp_sprintf(char *buf, const char *fmt, ... );
 
 extern const struct plugin_api * rb;
 
+#ifdef SIMULATOR
 
-#define SAMPLE_RATE SAMPR_44        /* 44100 */
+#define SAMPLE_RATE SAMPR_44  /* Required by Simulator */
+
+#elif ((CONFIG_PLATFORM & PLATFORM_HOSTED) || defined(CPU_MIPS))
+
+#define SAMPLE_RATE SAMPR_44 /* All MIPS and hosted targets are fast */
+
+#elif defined(CPU_ARM)
+
+/* Treat ARMv5+ as fast */
+#if (ARM_ARCH >= 5)
+#define SAMPLE_RATE SAMPR_44
+#else
+#define SAMPLE_RATE SAMPR_MIN_GE_22
+#endif
+
+#else /* !CPU_ARM */
+
+/* Treat everyone else as slow */
+#define SAMPLE_RATE HW_SAMPR_MIN_GE_22
+
+#endif /* !SIMULATOR */
 
 #define BUF_SIZE 4096*8
 #define NBUF   2