RAID/s390: remove invalid 'r' inline asm operand modifier

gcc silently ignores unsupported inline asm operand modifiers, effectively
turning '%r0' into '%0', but upcoming clang 9 complains about them:
lib/raid6/s390vx8.c:63:16: error: invalid operand in inline asm: 'VLM $2,$3,0,${1:r}'
        asm volatile ("VLM %2,%3,0,%r1"
                      ^

Clean up what look like a typo 'r' inline asm operand modifier usage.
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

lib/raid6/s390vx.uc

@@ -60,7 +60,7 @@ static inline void LOAD_DATA(int x, u8 *ptr)
 	typedef struct { u8 _[16 * $#]; } addrtype;
 	register addrtype *__ptr asm("1") = (addrtype *) ptr;
 
-	asm volatile ("VLM %2,%3,0,%r1"
+	asm volatile ("VLM %2,%3,0,%1"
 		      : : "m" (*__ptr), "a" (__ptr), "i" (x),
 			  "i" (x + $# - 1));
 }