x86/mwait-idle: stop exposing platform acronyms

x86/mwait-idle: stop exposing platform acronyms

This follows Linux commit de09cdd09fa1 ("intel_idle: stop exposing
platform acronyms in sysfs"), but their main justifications (sysfs
exposure and similarity with acpi-idle) don't apply to us. The field is
only used in a single printk() right now, but having the platform tags
there isn't useful either.

Requested-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>