Fix(PW DFT+U): add missing member variable assignments in init()

The develop branch refactored DFT+U to use explicit parameter passing,
but forgot to assign two member variables in the init() function:

1. this->npol was never set (defaulted to 1), causing incorrect Pauli
   matrix component iteration for nspin=4 calculations in
   cal_energy_correction().

2. this->device was never set (defaulted to empty string), causing the
   CPU code path in cal_occ_pw() to be skipped entirely. This resulted
   in the occupation matrix never being computed, leaving a zero/initial
   locale which produced wildly different PW DFT+U energies (~12-24 eV).

After this fix, all enabled 17_DS_DFTU test cases produce results
identical to accel-old branch (within numerical precision).

Author: dyzheng

source/source_lcao/module_dftu/dftu.cpp

@@ -85,6 +85,8 @@ void Plus_U::init(UnitCell& cell,
 #endif
 
     Plus_U::nspin = nspin;
+    this->npol = npol;
+    this->device = device;
 
     // mohan update 2025-11-06
     Plus_U::energy_u = 0.0;