gallium/swr: Param defaults for unhandled PIPE_CAPs

Without using this function, we fail the -Wswitch flag when compiling
the default debugoptimized mode in Meson

Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>
24 jobs for swr_screen_fix
Status Job ID Name Coverage
  Build+Test
canceled #111513
build:make-gallium-drivers-other

canceled #111512
build:make-gallium-drivers-radeonsi

canceled #111511
build:make-gallium-drivers-swr

canceled #111514
build:make-gallium-st-clover-llvm-39

canceled #111515
build:make-gallium-st-clover-llvm-4

canceled #111516
build:make-gallium-st-clover-llvm-5

canceled #111517
build:make-gallium-st-clover-llvm-6

canceled #111518
build:make-gallium-st-clover-llvm-7

canceled #111519
build:make-gallium-st-other

canceled #111510
build:make-loader-classic-dri

canceled #111509
build:make-vulkan

canceled #111505
build:meson-gallium-clover-llvm5

canceled #111506
build:meson-gallium-clover-llvm6

canceled #111507
build:meson-gallium-clover-llvm7

canceled #111504
build:meson-gallium-drivers-other

canceled #111503
build:meson-gallium-radeonsi

canceled #111508
build:meson-gallium-st-other

canceled #111502
build:meson-gallium-swr

canceled #111501
build:meson-glvnd

canceled #111500
build:meson-loader-classic-dri

canceled #111499
build:meson-vulkan

canceled #111521
build:scons-llvm

canceled #111520
build:scons-nollvm

canceled #111522
build:scons-swr