x86/asm: Remove thread_info.sysenter_return

It's no longer needed.

We could reinstate something like it as an optimization, which
would remove two cachelines from the fast syscall entry working
set. I benchmarked it, and it makes no difference whatsoever to
the performance of cache-hot compat syscalls on Sandy Bridge.

Signed-off-by: Andy Lutomirski <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/thread_info.h

···
 	__u32			cpu;		/* current CPU */
 	int			saved_preempt_count;
 	mm_segment_t		addr_limit;
-	void __user		*sysenter_return;
 	unsigned int		sig_on_uaccess_error:1;
 	unsigned int		uaccess_err:1;	/* uaccess failed */
 };

arch/x86/kernel/asm-offsets.c

···
 	OFFSET(IA32_SIGCONTEXT_ip, sigcontext_ia32, ip);
 
 	BLANK();
-	OFFSET(TI_sysenter_return, thread_info, sysenter_return);
-
-	BLANK();
 	OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe_ia32, uc.uc_mcontext);
 #endif