cmd_dhry.c: Use lldiv for vax_mips calculation as well

Since dhry_per_sec is a u64 we must also use lldiv here when working
with it.  Otherwise:
../lib/dhry/cmd_dhry.c:(.text.do_dhry+0xd8): undefined reference to `__udivdi3'

On some platforms.

Signed-off-by: Tom Rini <trini@konsulko.com>