fix: plat/marvell: a3700: Remove encryption password

fix: plat/marvell: a3700: Remove encryption password

According to "openssl" manual:
-K key
The actual key to use: this must be represented as a string
comprised only of hex digits. If only the key is specified,
the IV must additionally specified using the -iv option.
When both a key and a password are specified, the key given
with the -K option will be used and the IV generated from the
password will be taken.
It does not make much sense to specify both key and password.

This patch removes "-k 0" parameter from the encryption command
since we are already using "-K" and "-iv" for the key and IV.

Change-Id: Ia333cedaa3207e643c95d2ec7c229f50eeab96db
Signed-off-by: Konstantin Porotchkin <kostap@marvell.com>
Reviewed-on: http://vgitil04.il.marvell.com:8080/60745
Reviewed-by: Igal Liberman <igall@marvell.com>
Tested-by: iSoC Platform CI <ykjenk@marvell.com>
Reviewed-by: Sharon Habet <sharonh@marvell.com>