ARM: dts: msm: create OPPs for GPU device on 8909

Add GPU device node to dev-opp-list, so that the OPPs
(Operating Performance Points) for GPU gets created and
can be used by clients.

Change-Id: Ic5ec48fb90e335b3bae2c00a6b91edf95ea127a5
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>