defconfig: Enable GCM crypto library compilation

GCM crypto library is needed for GMAC support.
Define flag CONFIG_CRYPTO_GCM and set to 'y'(yes) to enable
compilation of the same.

Change-Id: I710fc81b3624bf484c6ba6f3cdd1bdb370e5bb33
CRs-Fixed: 2194089
Signed-off-by: Srinivas Dasari <dasaris@codeaurora.org>