package/freescale-imx/firmware-imx: fix the ahab-container name

package/freescale-imx/firmware-imx: fix the ahab-container name

After the firmware-imx bump to version 8.1.1 the following
error is observed when building freescale_imx8qxpmek_defconfig:

>> firmware-imx 8.1.1 Installing to images directory
cp /home/fabio/buildroot/output/build/firmware-imx-8.1.1/firmware/seco/ahab-container.img
/home/fabio/buildroot/output/images/ahab-container.img
cp: cannot stat
'/home/fabio/buildroot/output/build/firmware-imx-8.1.1/firmware/seco/ahab-container.img':
No such file or directory

In the firmware-imx-8.1.1 (and newer) the i.MX8QXP container image was
renamed to mx8qx-ahab-container.img, so fix it accordingly.

Fixes: 3ec818769d51 ("package/freescale-imx/firmware-imx: bump version to 8.1.1")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>