x86/pmtimer: move ACPI registers from PMTState to hvm_domain

x86/pmtimer: move ACPI registers from PMTState to hvm_domain

These registers (pm1a specifically) are not all specific to pm timer
and are accessed by non-pmtimer code (for example, sleep/power button
emulation).

The public name for save state structure is kept as 'pmtimer' to avoid
code churn with the expected changes in migration code. hvm_hw_acpi
name is introduced for internal use but when migration code is updated
hvm_hw_pmtimer will be renamed to hvm_hw_acpi.

No functional changes are introduced.

(While this file is being modified, also add emacs mode style rune)

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>