[bitops] Fix typo in test case

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

src/tests/bitops_test.c

 
 	/* Test clear_bit() */
 	clear_bit ( 0, bits );
-	ok ( bits[5] == 0x00 );
+	ok ( bits[0] == 0x00 );
 	bits[5] = 0xff;
 	clear_bit ( 42, bits );
 	ok ( bits[5] == 0xfb );