drm/amdgpu/display: fix FP handling in DCN30

Adjust the FP handling to avoid nested calls.

The nested calls cause the warning below
WARNING: CPU: 3 PID: 384 at arch/x86/kernel/fpu/core.c:129 kernel_fpu_begin

Fixes: 582e2ce5 ("drm/amdgpu/display: FP fixes for DCN3.x (v4)")
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>