amdgpu/pm: modify Powerplay API get_power_limit to use new pp_power enums

 updated {amd_pm_funcs}->get_power_limit() signature
 rewrote pp_get_power_limit to use new enums
 pp_get_power_limit now returns -EOPNOTSUPP for unknown power limit
 update calls to {amd_pm_funcs}->get_power_limit()

* Test Notes
* testing hardware was NAVI10 (tests SMU path)
** needs testing on VANGOGH
** needs testing on SMU < 11
** ie, one of
 TOPAZ, FIJI, TONGA, POLARIS10, POLARIS11, POLARIS12, VEGAM, CARRIZO,
 STONEY, VEGA10, VEGA12,VEGA20, RAVEN, BONAIRE, HAWAII

* Test
 AMDGPU_PCI_ADDR=`lspci -nn | grep "VGA\|Display" | cut -d " " -f 1`
 AMDGPU_HWMON=`ls -la /sys/class/hwmon | grep $AMDGPU_PCI_ADDR | cut -d " " -f 11`
 HWMON_DIR=/sys/class/hwmon/${AMDGPU_HWMON}

 lspci -nn | grep "VGA\|Display" ; \
 echo "=== power1 cap ===" ; cat $HWMON_DIR/power1_cap ;           \
 echo "=== power1 cap max ===" ; cat $HWMON_DIR/power1_cap_max ;   \
 echo "=== power1 cap def ===" ; cat $HWMON_DIR/power1_cap_default

Signed-off-by: Darren Powell <darren.powell@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>