s390: Use bool function return values of true/false not 1/0

Use the normal return values for bool functions
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/dma-mapping.h

@@ -42,7 +42,7 @@ static inline int dma_supported(struct device *dev, u64 mask)
 static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
 {
 	if (!dev->dma_mask)
-		return 0;
+		return false;
 	return addr + size - 1 <= *dev->dma_mask;
 }