Make perror("fopen") messages distinct

src/scarlett2-firmware.c

@@ -72,7 +72,7 @@ struct scarlett2_firmware_header *scarlett2_read_firmware_header(
 ) {
   FILE *file = fopen(fn, "rb");
   if (!file) {
-    perror("fopen");
+    perror("fopen firmware header");
     fprintf(stderr, "Unable to open %s\n", fn);
     return NULL;
   }
@@ -91,7 +91,7 @@ struct scarlett2_firmware_header *scarlett2_read_firmware_header(
 struct scarlett2_firmware_file *scarlett2_read_firmware_file(const char *fn) {
   FILE *file = fopen(fn, "rb");
   if (!file) {
-    perror("fopen");
+    perror("fopen firmware file");
     fprintf(stderr, "Unable to open %s\n", fn);
     return NULL;
   }

src/widget-sample-rate.c

@@ -46,7 +46,7 @@ static int get_sample_rate(struct sample_rate *data) {
 
   FILE *file = fopen(data->path, "r");
   if (!file) {
-    perror("fopen");
+    perror("fopen /proc/asound/cardN/stream0");
     return 0;
   }