riscv: Stop using kstack_end()

kstack_end() is a hack that is not correct on all arches.  The ancient
comment suggests that it masterfully works fully correctly on x86, for
example, but it's actually wrong on x86.

Since it could plausibly be correct on riscv, copy the implementation to
sh near its only call site.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
1 file changed