msm: ipa: fix to get bus scale handle

Bus scale handle is invalidated after every IPA driver probe.
Make a change to fetch bus scale handle just before calling ipa_init.

Change-Id: I58497d77e59202e9bac29a42223e544dc0361fba
Acked-by: Chaitanya Pratapa <cpratapa@qti.qualcomm.com>
Signed-off-by: Ravinder Konka <rkonka@codeaurora.org>