msm: kgsl: Attach secure context bank when mapping secure buffer

If secure context bank is not attached when mapping/unmapping
secure buffer, wakeup the device by taking active count. Once
map/unmap is finished remove active count to allow device to go
back to low power state. This is done to satisfy the current
trustzone/IOMMU driver requirement of secure context bank being
attached during map/unmap calls.

Change-Id: If974b86373dd82a4822016223eef30c9d5a07926
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>