defconfig: Enable default-key driver for msm8937_32go

This flag is needed for Metadata encryption to work:
CONFIG_DM_DEFAULT_KEY=y.

Test: 1. Device bootup with Metadata Encryption Enabled.
      2. Randomness test.

Change-Id: I872fd5614aeb9b4c5dd9c6be2dc1aa0cdbec1959
Signed-off-by: Vaibhav Agrawal <vagrawa@codeaurora.org>