watchdog/hpwdt: Refine hpwdt message for UV platform

watchdog/hpwdt: Refine hpwdt message for UV platform

The watchdog hardware the hpwdt driver uses was added to the UV
platform for UV_5, but the logging mentioned by this driver was not
added to the BIOS.  When the watchdog fires, the printed message had
the administrators and developers looking for non-existent log files,
and confused about whether a watchdog actually tripped.

Change the message that prints on UV platforms so it doesn't send the
user looking for non-existent logs.

To aid in any future debugging, include all 8 bits of the NMISTAT
register in the output, not just the two bits being used to determine
this was "mynmi".  And provide names to the bits in NMISTAT so the
code is easier to understand.

Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20260318155005.90271-1-steve.wahl@hpe.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>