Added benchmark for gravmag.prism
Added benchmark for gravmag.prism

eusoubrasileiro/fatiando_seismic,eusoubrasileiro/fatiando,rafaelmds/fatiando,victortxa/fatiando,fatiando/fatiando,mtb-za/fatiando,drandykass/fatiando,eusoubrasileiro/fatiando_seismic,victortxa/fatiando,drandykass/fatiando,cmeessen/fatiando,cmeessen/fatiando,santis19/fatiando,rafaelmds/fatiando,santis19/fatiando,fatiando/fatiando,eusoubrasileiro/fatiando,mtb-za/fatiando,eusoubrasileiro/fatiando