msm: ipa: initialize IPA->APPS pipe handle to an invalid value

When IPA->APPS WAN pipe handle is first initialized, it is set to
the value of 0. 0 might be a valid pipe handle, therefore, in cases
where pipe teardown is performed prior to initialization, the logic
might access un-allocated data.
This change initializes the pipe handle to an invalid value.

Change-Id: I3bd6310cda15da045c073f4a6c8b04358c251307
Acked-by: David Arinzon <darinzon@qti.qualcomm.com>
Signed-off-by: Sivan Reinstein <sivanr@codeaurora.org>