tracing: ftrace events for user faults and undefined instructions

New ftrace events (user_fault and undef_instr) for data, prefetch
or undefined instruction aborts. The new ftrace events are under
events/exception.

Change-Id: Iea328b71a1f623861cac9b45d858c3bbe09e1b82
Signed-off-by: Pushkar Joshi <pushkarj@codeaurora.org>