drm/amd/display: Disable ips before dc interrupt setting

[Why]
While in IPS2 an access to dcn registers is not allowed.
If interrupt results in dc call, we should disable IPS.

[How]
Safeguard register access in IPS2 by disabling idle optimization
before calling dc interrupt setting api.

Signed-off-by: Roman Li <Roman.Li@amd.com>
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>