drm/amdgpu: remove h from printk format specifier

See Documentation/core-api/printk-formats.rst.
h should no longer be used in the format specifier for printk.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>