ext4: remove readpage() check in ext4_mmap_file()

There is no kind of file which does not supply a page reading function.
Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/file.c

@@ -200,10 +200,6 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
 
 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	struct address_space *mapping = file->f_mapping;
-
-	if (!mapping->a_ops->readpage)
-		return -ENOEXEC;
 	file_accessed(file);
 	vma->vm_ops = &ext4_file_vm_ops;
 	return 0;