squashfs: Fix integer overflow in sqfs_inode_size()

squashfs: Fix integer overflow in sqfs_inode_size()

A carefully crafted squashfs filesystem can exhibit an extremly large
inode size and overflow the calculation in sqfs_inode_size().
As a consequence, the squashfs driver will read from wrong locations.

Fix by using __builtin_add_overflow() to detect the overflow.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>