[POWERPC] 4xx: Add mfspr/mtspr inline macros to 4xx bootwrapper

The 4xx bootwrapper occasionally needs to access SPR registers,
this adds mfspr/mtspr wrappers to it.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/boot/reg.h

@@ -16,6 +16,14 @@ static inline u32 mfpvr(void)
 	return pvr;
 }
 
+#define __stringify_1(x)	#x
+#define __stringify(x)		__stringify_1(x)
+
+#define mfspr(rn)	({unsigned long rval; \
+			asm volatile("mfspr %0," __stringify(rn) \
+				: "=r" (rval)); rval; })
+#define mtspr(rn, v)	asm volatile("mtspr " __stringify(rn) ",%0" : : "r" (v))
+
 register void *__stack_pointer asm("r1");
 #define get_sp()	(__stack_pointer)