drm/amdgpu: Release SDMAv4.4.2 ecc irq properly

Release ECC irq only if irq is enabled - only when RAS feature is enabled
ECC irq gets enabled.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>