rtc: m48t59: clean up m48t59_nvram_read()/m48t59_nvram_write()

The change removes redundant sysfs binary file boundary checks, since
this task is already done on caller side in fs/sysfs/file.c

Spinlock acquisition/release is moved out of the loop body to get
atomic states of NVRAM reading and writing operations.
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-m48t59.c

@@ -345,11 +345,12 @@ static ssize_t m48t59_nvram_read(struct file *filp, struct kobject *kobj,
 	ssize_t cnt = 0;
 	unsigned long flags;
 
-	for (; size > 0 && pos < pdata->offset; cnt++, size--) {
-		spin_lock_irqsave(&m48t59->lock, flags);
+	spin_lock_irqsave(&m48t59->lock, flags);
+
+	for (; cnt < size; cnt++)
 		*buf++ = M48T59_READ(cnt);
-		spin_unlock_irqrestore(&m48t59->lock, flags);
-	}
+
+	spin_unlock_irqrestore(&m48t59->lock, flags);
 
 	return cnt;
 }
@@ -365,11 +366,12 @@ static ssize_t m48t59_nvram_write(struct file *filp, struct kobject *kobj,
 	ssize_t cnt = 0;
 	unsigned long flags;
 
-	for (; size > 0 && pos < pdata->offset; cnt++, size--) {
-		spin_lock_irqsave(&m48t59->lock, flags);
+	spin_lock_irqsave(&m48t59->lock, flags);
+
+	for (; cnt < size; cnt++)
 		M48T59_WRITE(*buf++, cnt);
-		spin_unlock_irqrestore(&m48t59->lock, flags);
-	}
+
+	spin_unlock_irqrestore(&m48t59->lock, flags);
 
 	return cnt;
 }