fs/fat: debug-print file read position during file_fat_read_at()

In order to make the debug print in file_fat_read_at() a tad more useful,
show the offset the file is being read at alongside the filename.

Suggested-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 4efe8a3..4b722fc 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -1095,7 +1095,7 @@
 	if (ret)
 		goto out_free_both;
 
-	debug("reading %s\n", filename);
+	debug("reading %s at pos %llu\n", filename, pos);
 	ret = get_contents(&fsdata, itr->dent, pos, buffer, maxsize, actread);
 
 out_free_both: