tools: doimage: change the binary image alignment to 16
tools: doimage: change the binary image alignment to 16

Change the binary image alignment from 4 to 16.
The PKCS signature verification fails for unaligned images.

Change-Id: Ieb08dc3ea128790f542ad93e3c948117567a65af
Signed-off-by: Konstantin Porotchkin <4c7b7a89ae2c24f675bc0a94dfa7c7466687a3de@marvell.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware