um: remove unused variable

The buf variable is unused. Remove it.

Signed-off-by: Bartosz Golaszewski <[e-mail]>
Reviewed-by: Anton Ivanov <[e-mail]>
Acked-by: Anton Ivanov <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

arch/um/kernel/skas/uaccess.c

···
 static int do_op_one_page(unsigned long addr, int len, int is_write,
 		 int (*op)(unsigned long addr, int len, void *arg), void *arg)
 {
-	jmp_buf buf;
 	struct page *page;
 	pte_t *pte;
 	int n;