intel/isl: Refactor isl_calc_array_pitch_el_rows

intel/isl: Refactor isl_calc_array_pitch_el_rows

Over 90% of the function only applies to ISL_DIM_LAYOUT_GEN4_2D anyway
so we can just handle the other two as special cases at the top.  The
two "generic" cases below the switch only apply on gen9 and above and
only to 3D or CCS surfaces.  This implies that they only apply to
surfaces with ISL_DIM_LAYOUT_GEN4_2D.  Making them look generic is a
lie.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>