drm/msm/adreno: Assign msm_gpu->pdev earlier to avoid nullptrs

In the Linux kernel, the following vulnerability has been resolved:

drm/msm/adreno: Assign msm_gpu->pdev earlier to avoid nullptrs

There are some cases, such as the one uncovered by Commit 46d4efcccc68

("drm/msm/a6xx: Avoid a nullptr dereference when speedbin setting fails")

where

msm_gpu_cleanup() : platform_set_drvdata(gpu->pdev, NULL);

is called on gpu->pdev == NULL, as the GPU device has not been fully

initialized yet.

Turns out that there's more than just the aforementioned path that

causes this to happen (e.g. the case when there's speedbin data in the

catalog, but opp-supported-hw is missing in DT).

Assigning msm_gpu->pdev earlier seems like the least painful solution

to this, therefore do so.

Patchwork: https://patchwork.freedesktop.org/patch/602742/