fsi: core: Fix return of error values on failures

Currently the cfam_read and cfam_write functions return the provided
number of bytes given in the count parameter and not the error return
code in variable rc, hence all failures of read/writes are being
silently ignored. Fix this by returning the error code in rc.

Addresses-Coverity: ("Unused value")
Fixes: d1dcd678 ("fsi: Add cfam char devices")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jeremy Kerr <jk@ozlabs.org>
Link: https://lore.kernel.org/r/20210603122812.83587-1-colin.king@canonical.comSigned-off-by: Joel Stanley <joel@jms.id.au>

drivers/fsi/fsi-core.c

@@ -724,7 +724,7 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
 	rc = count;
  fail:
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static ssize_t cfam_write(struct file *filep, const char __user *buf,
@@ -761,7 +761,7 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
 	rc = count;
  fail:
 	*offset = off;
-	return count;
+	return rc;
 }
 
 static loff_t cfam_llseek(struct file *file, loff_t offset, int whence)