s390/uaccess: fix clear_user_pt()

The page table walker variant of clear_user() is supposed to copy the
contents of the empty zero page to user space.
However since 238ec4ef "[S390] zero page cache synonyms" empty_zero_page
is not anymore the page itself but contains the pointer to the empty zero
pages. Therefore the page table walker variant of clear_user() copied
the address of the first empty zero page and afterwards more or less
random data to user space instead of clearing the given user space range.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/lib/uaccess_pt.c

@@ -197,7 +197,7 @@ size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 
 static size_t clear_user_pt(size_t n, void __user *to)
 {
-	void *zpage = &empty_zero_page;
+	void *zpage = (void *) empty_zero_page;
 	long done, size, ret;
 
 	done = 0;