trace: Include <asm/asm-offsets.h> in trace_syscalls.c

Include <asm/asm-offsets.h> into trace_syscalls.c, to allow for
NR_syscalls to be automatically generated.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>