Bluetooth: qca: add missing firmware sanity checks

commit 2e4edfa1 upstream.

Add the missing sanity checks when parsing the firmware files before
downloading them to avoid accessing and corrupting memory beyond the
vmalloced buffer.

Fixes: 83e81961

 ("Bluetooth: btqca: Introduce generic QCA ROME support")
Cc: stable@vger.kernel.org	# 4.10
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>