uml: eliminate hz()

Eliminate hz() since its only purpose was to provide a kernel-space constant
to userspace code.  This can be done instead by providing the constant
directly through kernel_constants.h.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>