msm: kgsl: Do dispatcher init at first open

With eCP, we will no longer be using the dispatcher. And
we will have different first open functions depending on
whether eCP is enabled or disabled. Hence, move dispatcher
init to first open so that dispatcher is initialized only when
eCP is not enabled.

Change-Id: Ia65807dcfed65a4b810b886f71beb4c5ba30abb1
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>