dmaengine: ppc4xx: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20200311071606.4485-1-tiwai@suse.deSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/ppc4xx/adma.c

@@ -4303,7 +4303,7 @@ static ssize_t devices_show(struct device_driver *dev, char *buf)
 	for (i = 0; i < PPC440SPE_ADMA_ENGINES_NUM; i++) {
 		if (ppc440spe_adma_devices[i] == -1)
 			continue;
-		size += snprintf(buf + size, PAGE_SIZE - size,
+		size += scnprintf(buf + size, PAGE_SIZE - size,
 				 "PPC440SP(E)-ADMA.%d: %s\n", i,
 				 ppc_adma_errors[ppc440spe_adma_devices[i]]);
 	}