amdgpu/pm: Create shared array of power profile name strings

 == Description ==
 All the power profile modes use the same strings (or a subset of)
 Creating a public array of the strings will allow sharing rather than
 duplicating for each chip
 First patch only implements change for navi10, followup with other chips

 == Changes ==
 Create a declaration of the public array in kgd_pp_interface.h
 Define the public array in amdgpu_pm.c
 Modify the implementaiton of navi10_get_power_profile_mode to use new array

 == Test ==
 LOGFILE=pp_profile_strings.test.log
 AMDGPU_PCI_ADDR=`lspci -nn | grep "VGA\|Display" | cut -d " " -f 1`
 AMDGPU_HWMON=`ls -la /sys/class/hwmon | grep $AMDGPU_PCI_ADDR | awk '{print $9}'`
 HWMON_DIR=/sys/class/hwmon/${AMDGPU_HWMON}

 lspci -nn | grep "VGA\|Display"  > $LOGFILE
 FILES="pp_power_profile_mode "

 for f in $FILES
 do
   echo === $f === >> $LOGFILE
   cat $HWMON_DIR/device/$f >> $LOGFILE
 done
 cat $LOGFILE

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>