drm/amd/pm: Enable user min/max gfxclk on aldebaran

Aldebaran has fine grained DPM for GFXCLK. Instead of a discrete level,
user can specify a min/max range of GFXCLK for any profiling/tuning
purpose.This option is available only in manual performance level mode.
Select "manual" as power_dpm_force_performance_level and specify the
min/max range using pp_dpm_sclk sysfs node. User cannot specify a min/max
range outside of the default min/max range of the ASIC. If specified
outside the range, values will be bound by the default min/max range.

Ex: To use gfxclk min = 600MHz and max = 900MHz

echo manual > /sys/bus/pci/devices/.../power_dpm_force_performance_level
echo min 600 max 900 > /sys/bus/pci/devices/.../pp_dpm_sclk

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>