msm: kgsl: Move the system PM operations to adreno

The system power management functions (suspend/resume) are currently
registered with the adreno device but implemented at the KGSL level
which requires function hooks for the actual adreno functionality.

Move the functions back to adreno where they belong, get rid of the
function hooks and remove the legacy suspend/resume handlers that
we haven't needed in years.

Change-Id: Ic0dedbad4a09f165ffd9707e66c45e5b516962e3
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>