m68k: Add helper function handle_kernel_fault()

Add helper function handle_kernel_fault() in signal.c, so frame_extra_sizes
can become static, and to avoid future code duplication.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h
index 278c69b..f111b02 100644
--- a/arch/m68k/include/asm/processor.h
+++ b/arch/m68k/include/asm/processor.h
@@ -113,6 +113,8 @@
 	wrusp(usp);
 }
 
+extern int handle_kernel_fault(struct pt_regs *regs);
+
 #else
 
 /*