isapnp: switch to fixed_size_llseek()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/pnp/isapnp/proc.c

diff --git a/drivers/pnp/isapnp/proc.c b/drivers/pnp/isapnp/proc.c
index 2365ef3..5edee64 100644
--- a/drivers/pnp/isapnp/proc.c
+++ b/drivers/pnp/isapnp/proc.c
@@ -29,27 +29,7 @@
 
 static loff_t isapnp_proc_bus_lseek(struct file *file, loff_t off, int whence)
 {
-	loff_t new = -1;
-	struct inode *inode = file_inode(file);
-
-	mutex_lock(&inode->i_mutex);
-	switch (whence) {
-	case 0:
-		new = off;
-		break;
-	case 1:
-		new = file->f_pos + off;
-		break;
-	case 2:
-		new = 256 + off;
-		break;
-	}
-	if (new < 0 || new > 256)
-		new = -EINVAL;
-	else
-		file->f_pos = new;
-	mutex_unlock(&inode->i_mutex);
-	return new;
+	return fixed_size_llseek(file, off, whence, 256);
 }
 
 static ssize_t isapnp_proc_bus_read(struct file *file, char __user * buf,