dsp: ion: Remove smmu initialization

SMMU initialization is not required to be done in client
probe process. SMMU framework takes care of creating
domain and attaching device. Remove related code from
audio ion driver.

Change-Id: I3756c5abb7488afb43e20fae698c7008461a18cb
Signed-off-by: Meng Wang <mengw@codeaurora.org>