drm/amdgpu: Fix ISP segfault issue in kernel v7.0

drm/amdgpu: Fix ISP segfault issue in kernel v7.0

Add NULL pointer checks for dev->type before accessing
dev->type->name in ISP genpd add/remove functions to
prevent kernel crashes.

This regression was introduced in v7.0 as the wakeup sources
are registered using physical device instead of ACPI device.
This led to adding wakeup source device as the first child of
AMDGPU device without initializing dev-type variable, and
resulted in segfault when accessed it in the amdgpu isp driver.

Fixes: 057edc58aa59 ("ACPI: PM: Register wakeup sources under physical devices")
Suggested-by: Bin Du <Bin.Du@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Pratap Nirujogi <pratap.nirujogi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>