Derivative of 6-phenyl-2,7-naphthyridine-3-carboxylic acid hydrazide with the chemical name of 2,4-dihydroxy-benzylidene hydrazide of 8-ethoxy-6-phenyl-4-hydroxy-1,2-dihydro-1-oxo- 2,7-naphthyridine-3-carboxylic acid and process for the preparation thereof