Fixed type cast error in fmax() in hydro_cuda.cu
Fixed type cast error in fmax() in hydro_cuda.cu

cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,evaneschneider/cholla