entry: Expose helpers to migrate TIF to SYSCALL_WORK flags

With the goal to split the syscall work related flags into a separate
field that is architecture independent, expose transitional helpers that
resolve to either the TIF flags or to the corresponding SYSCALL_WORK
flags.  This will allow architectures to migrate only when they port to
the generic syscall entry code.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-3-krisman@collabora.com