Merge the thread_info definition into one structure definition for both arches.

The __u32 is equal to unsigned long for 32 bit.

sysenter_return is used both for the IA32 emulation for 64 and x86_32.
Avoid complicated #ifdef by simply always including it.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>