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: I189680c588d31fd2549d08094208e55dce45ffbf
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>