msm: ADSPRPC: Update driver to be part of kernel image

Remove the default to enable the driver to be built as
part of the kernel image.

Change-Id: I3e18aa5bc34cf1451a982bdc4c3f717e905793c8
Acked-by: Sathish Ambley <sambley@qti.qualcomm.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>