ARM: 7595/1: syscall: rework ordering in syscall_trace_exit

syscall_trace_exit is currently doing things back-to-front; invoking
the audit hook *after* signalling the debugger, which presents an
opportunity for the registers to be re-written by userspace in order to
bypass auditing constaints.

This patch fixes the ordering by moving the audit code first and the
tracehook code last. On the face of it, it looks like
current_thread_info()->syscall may be incorrect for the sys_exit
tracepoint, but that's actually not an issue because it will have been
set during syscall entry and cannot have changed since then.

Reported-by: Andrew Gabbasov <Andrew_Gabbasov@mentor.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>