msm: ipa3: Fix to avoid accessing of uninitialized structure

Added code changes to check ipa3_ctx initilized or not
during bootup in sdm670.

Change-Id: I03e5b8de30c77da140e9575c2315b0878cf5363c
Acked-by: Ashok Vuyyuru <avuyyuru@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>