Relocate IMAGE_INDEX_MAX and add notes about usage.

src/ZuluSCSI_config.h

@@ -56,6 +56,9 @@
 #define HDIMG_BLK_POS 5                 // Position to embed block size numbers
 #define MAX_FILE_PATH 64                // Maximum file name length
 
+// Image definition options
+#define IMAGE_INDEX_MAX 9               // Maximum number of 'IMG0' style statements parsed
+
 // SCSI config
 #define NUM_SCSIID  8          // Maximum number of supported SCSI-IDs (The minimum is 0)
 #define NUM_SCSILUN 1          // Maximum number of LUNs supported     (Currently has to be 1)

src/ZuluSCSI_disk.h

@@ -40,8 +40,6 @@ extern "C" {
 #include <scsi.h>
 }
 
-#define IMAGE_INDEX_MAX 9
-
 // Extended configuration stored alongside the normal SCSI2SD target information
 struct image_config_t: public S2S_TargetCfg
 {