[uaccess] Remove redundant copy_from_user() and copy_to_user()

Remove the now-redundant copy_from_user() and copy_to_user() wrapper
functions.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/blocktrans.c

@@ -31,6 +31,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  */
 
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 #include <assert.h>
 #include <ipxe/iobuf.h>