timer(4/sparc64): remove driver

timer(4/sparc64): remove driver

The timer(4/sparc64) driver was effectively disabled during the
previous release.  Nobody has come forward asking for it to be adapted
to work with the new clockintr framework, so it's time to remove the
driver from the tree.

As of today, if you want to run OpenBSD on SPARC v9 hardware, that
hardware needs to sport either %tick and %tick_compare (%asr23), or
%stick (%asr24) and %stick_compare (%asr25).

All Sun/Oracle SPARC v9 hardware meets these conditions, from the
UltraSPARC I onward.

Most HAL/Fujitsu SPARC v9 hardware meets these conditions, from the
SPARC64 III onward.  The only HAL/Fujitsu hardware that might not have
%tick_compare are the HAL SPARC64 I and SPARC64 II, for which I can
find no documentation.  However, those processors are currently
unsupported by OpenBSD for other reasons, so their support status is
unchanged by the removal of this driver.

With help from miod@.

Link: https://marc.info/?l=openbsd-tech&m=167898759928206&w=2
"after unlock" deraadt@, ok mlarkin@ miod@