softoff: Fix the CI error

The CI for new patch set report errors in softoff code.

'''
../softoff/softoff.cpp: In member function 'int pldm::SoftPowerOff::getSensorInfo()':
../softoff/softoff.cpp:263:14: error: 'pdr' may be used uninitialized [-Werror=maybe-uninitialized]
  263 |         auto possibleStatesStart = pdr->possible_states;
      |              ^~~~~~~~~~~~~~~~~~~
../softoff/softoff.cpp:249:32: note: 'pdr' was declared here
  249 |         pldm_state_sensor_pdr* pdr;
cc1plus: all warnings being treated as errors
'''

Update code to fix that.

Signed-off-by: ThuBaNguyen <thu@os.amperecomputing.com>
Change-Id: Ib9df9f79978941ebad62164866cc688412a08922