ARM: dts: msm: Enable 256 bit key support for sdm670

Userdata security depends upon disk encryption key
strenght. Larger the key size stronger is the encryption
and more difficult and time taken it will be for any
brute force attack to decrypt the user content.

Change-Id: Ib21049220dcb2034709da2cc1d770075dec89f01
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>