microblaze: Add missing declaration for die and _exception func

This change remove sparse errors.
Signed-off-by: NMichal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/exceptions.h

@@ -61,6 +61,9 @@
 asmlinkage void full_exception(struct pt_regs *regs, unsigned int type,
 							int fsr, int addr);
 
+void die(const char *str, struct pt_regs *fp, long err);
+void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr);
+
 #if defined(CONFIG_XMON)
 extern void xmon(struct pt_regs *regs);
 extern int xmon_bpt(struct pt_regs *regs);