Remove definitions from headers to avoid linking errors

Those were causing linking errors since they were defined multiple times
(whenever it was included somewhere else). ChannelBankIndex was removed
since it was not used anywhere. product_id is already defined on gdigi.c
so it was marked as extern.

gdigi.h

@@ -42,7 +42,7 @@ gboolean debug_flag_is_set (debug_flags_t flag);
 #define GNX_CABINET_WARP 263
 #define GNX_CHANNEL_FS_MODE 264
 
-unsigned char product_id;
+extern unsigned char product_id;
 
 enum {
   GNX3K_WAH_TYPE_CRY = 129,
@@ -1120,7 +1120,7 @@ enum {
     GENETX_CHANNEL1_CUSTOM = 2,
     GENETX_CHANNEL2_CUSTOM = 3,
     GENETX_CHANNEL_CURRENT = 4
-} ChannelBankIndex;
+};
 
 typedef struct {
     int version;