iwlwifi: fw: harden page loading code

commit 9039d985811d5b109b58b202b7594fd24e433fed upstream.

The page loading code trusts the data provided in the firmware images
a bit too much and may cause a buffer overflow or copy unknown data if
the block sizes don't match what we expect.

To prevent potential problems, harden the code by checking if the
sizes we are copying are what we expect.

Cc: stable@vger.kernel.org
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>