Allow the user program to specify both ASYNC and SYNC TCF modes by
repurposing the existing constants as bitfields. This will allow the
kernel to select one of the modes on behalf of the user program. With
this patch the kernel will always select async mode, but a subsequent
patch will make this configurable.

Link: https://linux-review.googlesource.com/id/Icc5923c85a8ea284588cc399ae74fd19ec291230Signed-off-by: NPeter Collingbourne <pcc@google.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210727205300.2554659-3-pcc@google.comAcked-by: NWill Deacon <will@kernel.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>