muen-timer: Set correct clock event feature flags

Use CLOCK_EVT_FEAT_ONESHOT to set clock event feature flag. The
CLOCK_EVT_MODE_ONESHOT enum value has a different value than the flag
and must not be used in this context.
muen-timer: Initialize clock event driver earlier

This makes the clock event device available during module
initialization, e.g. Intel's e1000e driver.
muen-timer: Initial clock event using timer page

Use Muen subject timer page to set next event. Only one-shot mode is
supported. The address of the timer page is set to the memory region
with name "timer".
muen-timer: Warn when setting unsupported mode

Also disable timer when clock event mode is set to CLOCK_EVT_MODE_UNUSED
or CLOCK_EVT_MODE_SHUTDOWN.
muen-timer: Raise priority of muen-timer clock event driver

Make sure that Muen Timer is used as clock event device, if present.
muen-timer: Register TSC tickrate as clockevent freq

Use the muen_get_tsc_khz() function to retrieve the host's TSC frequency
and register it as the clockevent frequency.
muen-timer: Declare UINT_MAX as max_delta_ticks

The value argument on the timer page is uint64_t and designates an
absolute time in ticks. Therefore allow UINT_MAX as maximum relative
time in ticks.
muen-timer: Use rdtsc to set timer page value

Set the absolute time in ticks the next event is supposed to fire by
adding the current TSC value to the delta.
muen-timer: Add module information and update copyright
muen-timer: Update Kconfig entry
muen-timer: Drop obsolete Muen clocksource timer
muen: Update module author and copyright info