Use correct endianness for encryption keys

From ICE 3.0 onwards the keys are used in little endian format
but legacy ICE driver in trustzone reverses the endianness. So reverse
the endianness of keys before passing it to trusted ICE driver.

Change-Id: I5c343054526d43234d5ab1f072a199c6f4203e5a
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>