drm/amdgpu/soc21: fix xclk for APUs

drm/amdgpu/soc21: fix xclk for APUs

commit e7fbff9e7622a00c2b53cb14df481916f0019742 upstream.

The reference clock is supposed to be 100Mhz, but it
appears to actually be slightly lower (99.81Mhz).

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/14451
Reviewed-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 637fee3954d4bd509ea9d95ad1780fc174489860)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>