USER-DPD: Update the header files to properly document all error statements

Patch by Jim Larentzos.  Applied by Tim Mattox.

src/USER-DPD/fix_eos_cv.h

@@ -50,6 +50,10 @@ Self-explanatory.  Check the input script syntax and compare to the
 documentation for the command.  You can use -echo screen as a
 command-line option when running LAMMPS to see the offending line.
 
+E:  FixEOScv requires atom_style with internal temperature and energies (e.g. dpd)
+
+Self-explanatory.
+
 E: EOS cv must be > 0.0
 
 The constant volume heat capacity must be larger than zero.

src/USER-DPD/fix_eos_table.h

@@ -92,6 +92,10 @@ E: eos/table values are not increasing
 
 The EOS must be a monotonically, increasing function
 
+E:  FixEOStable requires atom_style with internal temperature and energies (e.g. dpd)
+
+Self-explanatory.
+
 E: Internal temperature < zero
 
 Self-explanatory.  EOS may not be valid under current simulation conditions.