[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/drivers/linux/slirp.c

@@ -18,6 +18,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <errno.h>
 #include <ipxe/netdevice.h>
 #include <ipxe/ethernet.h>