android: Change gralloc_handle_t members to be fixed width

In order to lessen future alignment issues, lets switch to
fixed width integers where possible.

This excludes the data_owner since it is a pid_t which
in theory could be larger than 32 bits.

Signed-off-by: Robert Foss <robert.foss@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>