asm-generic: Provide generic TIF infrastructure

asm-generic: Provide generic TIF infrastructure

Common TIF bits do not have to be defined by every architecture. They can
be defined in a generic header.

That allows adding generic TIF bits without chasing a gazillion of
architecture headers, which is again a unjustified burden on anyone who
works on generic infrastructure as it always needs a boat load of work to
keep existing architecture code working when adding new stuff.

While it is not as horrible as the ignorance of the generic entry
infrastructure, it is a welcome mechanism to make architecture people
rethink their approach of just leaching generic improvements into
architecture code and thereby making it accumulatingly harder to maintain
and improve generic code. It's about time that this changes.

Provide the infrastructure and split the TIF space in half, 16 generic and
16 architecture specific bits.

This could probably be extended by TIF_SINGLESTEP and BLOCKSTEP, but those
are only used in architecture specific code. So leave them alone for now.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>