powerpc/traps: add NOKPROBE_SYMBOL for sreset and mce

These NMIs could fire any time including inside kprobe code, so
exclude them from kprobes.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210130130852.2952424-19-npiggin@gmail.com

arch/powerpc/kernel/traps.c

@@ -517,6 +517,7 @@ void system_reset_exception(struct pt_regs *regs)
 
 	/* What should we do here? We could issue a shutdown or hard reset. */
 }
+NOKPROBE_SYMBOL(system_reset_exception);
 
 /*
  * I/O accesses can cause machine checks on powermacs.
@@ -843,6 +844,7 @@ void machine_check_exception(struct pt_regs *regs)
 bail:
 	if (nmi) nmi_exit();
 }
+NOKPROBE_SYMBOL(machine_check_exception);
 
 void SMIException(struct pt_regs *regs)
 {