diag: Silence section mismatches

The diag code is improperly using the __init/__exit markings and
calling functions that don't exist at certain times. Remove the
init and exit markings as these functions are used from both init
and exit context. Note another solution is possible where init
functions are only called from init functions but that would
break the error handling here so we just remove the markings for
simplicity.

Change-Id: I86677b74676871504b1b47f21c92002757ae194a
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>