Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
index bd9ba8d..84b4cfe 100644
--- a/arch/powerpc/include/asm/nmi.h
+++ b/arch/powerpc/include/asm/nmi.h
@@ -14,4 +14,6 @@
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif
 
+extern void hv_nmi_check_nonrecoverable(struct pt_regs *regs);
+
 #endif /* _ASM_NMI_H */