clover: Pass buffer offsets to the driver in set_global_binding() v3

The offsets will be stored in the handles parameter.  This makes
it possible to use sub-buffers.

v2:
  - Style fixes
  - Add support for constant sub-buffers
  - Store handles in device byte order

v3:
  - Use endian helpers

Reviewed-by: Francisco Jerez <currojerez@riseup.net>
4 files changed