ARM: dts: msm: Remove GDSC and update clocks for GPU SMMU on 8909.

8909 GPU SMMU is always ON domain and does not have any
regulator to vote before accessing its registers.
Hence remove GX GDSC handle from GPU SMMU DT node.

Also use proper clocks for register programming of GPU SMMU.

Fixes: 6aa9a864 ("ARM: dts: msm: Add kgsl smmu support for MSM8909w")
Change-Id: I2afeec6abb06733772dd307bae81149a63bfe005
Signed-off-by: Rajesh Kemisetti <rajeshk@codeaurora.org>