gallium: Add PIPE_SHADER_CAP_FP16

Denotes native half precision float operations capability
v2: PIPE_CAP_HALFS -> PIPE_SHADER_CAP_FP16
    fix indentation

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
16 files changed