btrfs-progs: fix clang warning in array length calculation in print_h…

…eader_info()

Clang 19.1.6 reports:

  kernel-shared/print-tree.c:1346:38: warning: variable length array
    folded to constant array as an extension [-Wgnu-folding-constant]
    1346 |         char csum_str[2 * BTRFS_CSUM_SIZE + strlen(" csum 0x") + 1];

Signed-off-by: David Sterba <dsterba@suse.com>

kernel-shared/print-tree.c

@@ -1343,7 +1343,7 @@ static void print_header_info(struct extent_buffer *eb, unsigned int mode)
 	u64 flags;
 	u32 nr;
 	u8 backref_rev;
-	char csum_str[2 * BTRFS_CSUM_SIZE + strlen(" csum 0x") + 1];
+	char csum_str[2 * BTRFS_CSUM_SIZE + 8 /* strlen(" csum 0x") */ + 1];
 	int i;
 	int csum_size = fs_info->csum_size;