mali_kbase: platform: secure: Disable ifpo in secure mode

When the GPU is in secure mode, disable inter-frame
power off in order to ensure consistency. This is a
more appropriate solution than disabling secure mode
just prior to an ifpo and then re-enabling it before
powering back on.

Bug: 190727516
Test: run cts-dev --include-filter "CtsDeqpTestCases dEQP-VK.protected_memory.*"
Signed-off-by: Sidath Senanayake <sidaths@google.com>
Change-Id: Id3ec1da1294e9d88c5f9c109ebe4093e2874b5ba