drm/amdgpu: fix IH ring allocation for bus addresses (v2)

Use pci_alloc_consistent rather than kzalloc since we
need 256 byte aligned memory for the ring buffer.

v2: fix copy paste typo in free function noticed
by Jammy.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=91749



Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org