drivers: rpmsg: Add smd driver module at post core init

Order qcom smd driver, rpm smd driver modules initialization
at post core init stage to make available regulators and clocks.

Change-Id: If377decb914bb5f2c2ddfc05efe0ec886b9ded15
Signed-off-by: Sudharsan Reddy Yettapu <syepattu@codeaurora.org>
Signed-off-by: Sivasri Kumar Vanka <sivasri@codeaurora.org>