hwrng: s390 - replace snprintf in show functions with sysfs_emit

coccicheck complains about the use of snprintf() in sysfs show functions.

Fix the following coccicheck warning:
drivers/char/hw_random/s390-trng.c:114:8-16: WARNING: use scnprintf or sprintf.
drivers/char/hw_random/s390-trng.c:122:8-16: WARNING: use scnprintf or sprintf.

Use sysfs_emit instead of scnprintf or sprintf makes more sense.
Signed-off-by: Qing Wang <wangqing@vivo.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/s390-trng.c

@@ -111,7 +111,7 @@ static ssize_t trng_counter_show(struct device *dev,
 #if IS_ENABLED(CONFIG_ARCH_RANDOM)
 	u64 arch_counter = atomic64_read(&s390_arch_random_counter);
 
-	return snprintf(buf, PAGE_SIZE,
+	return sysfs_emit(buf,
 			"trng:  %llu\n"
 			"hwrng: %llu\n"
 			"arch:  %llu\n"
@@ -119,7 +119,7 @@ static ssize_t trng_counter_show(struct device *dev,
 			dev_counter, hwrng_counter, arch_counter,
 			dev_counter + hwrng_counter + arch_counter);
 #else
-	return snprintf(buf, PAGE_SIZE,
+	return sysfs_emit(buf,
 			"trng:  %llu\n"
 			"hwrng: %llu\n"
 			"total: %llu\n",