Update source files for NEP installation script (deepmodeling#6871)

Author: ZhouXY-PKU

toolchain/scripts/stage4/install_nep.sh

@@ -63,7 +63,7 @@ CXXFLAGS = -O2 -fPIC -std=c++11
 INCLUDES = -I./src
 
 # Source files
-SRCS = ./src/nep.cpp ./src/ewald.cpp ./src/neighbor.cpp
+SRCS = ./src/nep.cpp ./src/ewald_nep.cpp ./src/neighbor_nep.cpp
 
 # Object files
 OBJS = \$(SRCS:.cpp=.o)
@@ -154,4 +154,4 @@ load "${BUILDDIR}/setup_nep"
 write_toolchain_env "${INSTALLDIR}"
 
 cd "${ROOTDIR}"
-report_timing "nep"
+report_timing "nep"