isl: Fix isl_surf_get_image_offset_sa for gen4_3d layout
isl: Fix isl_surf_get_image_offset_sa for gen4_3d layout

Bug found by unit test
test_bdw_3d_r8g8b8a8_unorm_256x256x256_levels09_tiley0.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler