The 'hw.acpi.suspend_state' sysctl knob was re-introduced with a bug.
Its handler, acpi_suspend_state_sysctl(), expects the ACPI softc in
'arg1', but the knob was registered with NULL there. This causes
a panic (NULL dereference) when reading the knob if the suspend state
has been set to S1 or S2 or equivalently the suspend sleep type to
STANDBY.
Fix it by passing the ACPI softc as 'arg1' when registering the knob.
Fixes: 9e1e29bd5ec6 ("acpi: Add back hw.acpi.suspend_state sysctl")
Sponsored by: The FreeBSD Foundation