R600: Add 64-bit v2f32/v2i32 store

Signed-off-by: Dmitry Cherkassov <dcherkassov@gmail.com>
R600: Add test for 64-bit v2f32/v2i32

Added tests for checking v2f32/v2i32 load, store and element extract

Signed-off-by: Dmitry Cherkassov <dcherkassov@gmail.com>