x86/platform/uv: Remove support for UV1 platform from uv_bau

UV1 is not longer supported.

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200713212955.083309377@hpe.com