Fix wt_200k_G.c "initializer element is not constant" error with GCC …

…< 8.1

Building with GCC < 8.1 would give the following error:

arm-wt-22k/lib_src/wt_200k_G.c:114:5: error: initializer element is not constant
     0x00200000 | sampleRate,
     ^~~~~~~~~~
arm-wt-22k/lib_src/wt_200k_G.c:114:5: note: (near initialization for 'easSoundLib.libAttr')

See also:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69960#c18

Using an 'enum' for the 'sampleRate' value is enough for older GCC releases.

arm-wt-22k/lib_src/wt_200k_G.c

@@ -99,19 +99,20 @@ const S_BANK eas_banks[] =
  *----------------------------------------------------------------------------
 */
 
+// Can't be a 'const EAS_U32' before GCC 8.1
 #ifdef _SAMPLE_RATE_44100
-const EAS_U32 sampleRate = 0xAC44;
+enum { sampleRate = 0xAC44 };
 #else
-const EAS_U32 sampleRate = 0x5622;
+enum { sampleRate = 0x5622 };
 #endif
 
 const S_EAS easSoundLib = {
     0x01534145,
 
 #if defined (_8_BIT_SAMPLES)
-    0x00100000 | sampleRate,
+    0x00100000 | (EAS_U32)sampleRate,
 #else //_16_BIT_SAMPLES
-    0x00200000 | sampleRate,
+    0x00200000 | (EAS_U32)sampleRate,
 #endif
 
     eas_banks,