drm/msm: adreno: fix deferencing ifpc_reglist when not declared

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

drm/msm: adreno: fix deferencing ifpc_reglist when not declared

On plaforms with an a7xx GPU not supporting IFPC, the ifpc_reglist

if still deferenced in a7xx_patch_pwrup_reglist() which causes

a kernel crash:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008

...

pc : a6xx_hw_init+0x155c/0x1e4c [msm]

lr : a6xx_hw_init+0x9a8/0x1e4c [msm]

...

Call trace:

a6xx_hw_init+0x155c/0x1e4c [msm] (P)

msm_gpu_hw_init+0x58/0x88 [msm]

adreno_load_gpu+0x94/0x1fc [msm]

msm_open+0xe4/0xf4 [msm]

drm_file_alloc+0x1a0/0x2e4 [drm]

drm_client_init+0x7c/0x104 [drm]

drm_fbdev_client_setup+0x94/0xcf0 [drm_client_lib]

drm_client_setup+0xb4/0xd8 [drm_client_lib]

msm_drm_kms_post_init+0x2c/0x3c [msm]

msm_drm_init+0x1a4/0x228 [msm]

msm_drm_bind+0x30/0x3c [msm]

...

Check the validity of ifpc_reglist before deferencing the table

to setup the register values.

Patchwork: https://patchwork.freedesktop.org/patch/688944/