drm/amd/pm: Remove arcturus min power limit

As per power team, there is no need to impose a lower bound on arcturus
power limit. Any unreasonable limit set will result in frequent
throttling.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org