msm: ipa: tethering bridge: add support for power collapse

Adds support for power collapse. The code uses resource managers'
inactivity timer to request the BRIDGE_PROD resource before every
packet send, and release it afterward, using a dedicated workqueue.

Change-Id: Ib67ebe981ff9bab5ef7c6d6f271387504611366e
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>