drm/amd/display: Simplify dcn35_is_ips_supported()

[WHAT & HOW]
The variable "ips_supported" is redundant and we can return from
dcn35_smu_get_ips_supported directly.

This fixes 1 UNUSED_VALUE issue reported by Coverity.

Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>