drm/radeon: drop setting UPLL to sleep mode

commit a17d4996e051e78d164989b894608cf37cd5110b upstream.

Just keep it working, seems to fix some PLL problems.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=73378



Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>