powerpc: mtspr/mtmsr should take an unsigned long

Add a cast in case the caller passes in a different type, as it would
if mtspr/mtmsr were functions.

Previously, if a 64-bit type was passed in on 32-bit, GCC would bind the
constraint to a pair of registers, and would substitute the first register
in the pair in the asm code.  This corresponds to the upper half of the
64-bit register, which is generally not the desired behavior.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/reg.h

@@ -1024,13 +1024,16 @@
 #define mtmsrd(v)	__mtmsrd((v), 0)
 #define mtmsr(v)	mtmsrd(v)
 #else
-#define mtmsr(v)	asm volatile("mtmsr %0" : : "r" (v) : "memory")
+#define mtmsr(v)	asm volatile("mtmsr %0" : \
+				     : "r" ((unsigned long)(v)) \
+				     : "memory")
 #endif
 
 #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)\
+#define mtspr(rn, v)	asm volatile("mtspr " __stringify(rn) ",%0" : \
+				     : "r" ((unsigned long)(v)) \
 				     : "memory")
 
 #ifdef __powerpc64__