spirv: add support for doubles to OpSpecConstant

v2 (Jason):
- Fix indent in radv change
- Add vtn_u64_literal() helper to take 64 bits (Jason)

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
5 files changed