albumart: use a separate variable for temporary pointer storage

Re-using the same one confuses some static code analyzers, and
is a bit less readable.

albumart.c

@@ -267,7 +267,7 @@ check_for_album_file(const char *path)
 	struct album_art_name_s *album_art_name;
 	image_s *imsrc = NULL;
 	int width=0, height=0;
-	char *art_file;
+	char *art_file, *p;
 	const char *dir;
 	struct stat st;
 	int ret;
@@ -289,19 +289,19 @@ check_for_album_file(const char *path)
 	if( ret != 0 )
 	{
 		strncpyt(file, path, sizeof(file));
-		art_file = strrchr(file, '.');
-		if( art_file )
+		p = strrchr(file, '.');
+		if( p )
 		{
-			strcpy(art_file, ".jpg");
+			strcpy(p, ".jpg");
 			ret = access(file, R_OK);
 		}
 		if( ret != 0 )
 		{
-			art_file = strrchr(file, '/');
-			if( art_file )
+			p = strrchr(file, '/');
+			if( p )
 			{
-				memmove(art_file+2, art_file+1, file+MAXPATHLEN-art_file-2);
-				art_file[1] = '.';
+				memmove(p+2, p+1, file+MAXPATHLEN-p-2);
+				p[1] = '.';
 				ret = access(file, R_OK);
 			}
 		}