defconfig: 8226: Enable ADSP RPC driver

The ADSP RPC driver allows for clients to make remote method
invocations across processor boundary to DSP processor. Enable
this driver for MSM8226.

Change-Id: Id5312df1715b88129479023d189d4ef18afbe3e7
Acked-by: Sathish Ambley <sambley@qti.qualcomm.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>