msm: ipa: add api for getting IPA pdev

Add API intended for IPA kernel tests.
This API will allow kernel tests to use IPA driver
pdev struct by returning a pointer to this struct.

CRs-Fixed: 1077422
Change-Id: Ideeaa89f15b8895ce7256fed9f614d5c39ef105f
Signed-off-by: Amir Levy <alevy@codeaurora.org>
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>