x86/platform/uv: Remove remaining BUG_ON() and BUG() calls

Replace BUG and BUG_ON with WARN_ON_ONCE and carry on as best as we
can.

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20230519190752.3297140-8-steve.wahl%40hpe.com