Redo r339563: Remove joy(4) driver.
This driver was marked as gone in 12. We're at 13 now. Remove it.
Data from nycbug's dmesg cache shows only one potential user,
suggesting it never was used much. However, even though this device
has been obsolete for 15 years at least, sys/joystick.h is included in
a number of graphics packages still, so that remains. A full exprun
is needed before that can be removed.
Differential Revision: https://reviews.freebsd.org/D17629