drm/amdgpu: Fix mutex lock from atomic context.

Problem:
amdgpu_ras_reserve_bad_pages was moved to amdgpu_ras_reset_gpu
because writing to EEPROM during ASIC reset was unstable.
But for ERREVENT_ATHUB_INTERRUPT amdgpu_ras_reset_gpu is called
directly from ISR context and so locking is not allowed. Also it's
irrelevant for this partilcular interrupt as this is generic RAS
interrupt and not memory errors specific.

Fix:
Avoid calling amdgpu_ras_reserve_bad_pages if not in task context.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>