adv7481: Add suspend and resume handler functions

Add suspend and resume handler to be called from power management
framework for driver to release clock votes prior to device goes
into sleep state. Driver requests for the necessary resources in
resume handler

CRs-Fixed: 1062576
Change-Id: Iff9e7ed7b7918f9a371453a020086f22e844d7e4
Signed-off-by: Terence Ho <terenceh@codeaurora.org>