arch/x86_64: make ARCH_INTEL64_HPET_ALARM buildable.

ARCH_INTEL64_HPET_ALARM is one of the three members of the "System Timer
Source" choice, but selecting it does not build.  Taking qemu-intel64:nsh on
master and moving the choice off ARCH_INTEL64_TSC_DEADLINE onto it:

  intel64/intel64_hpet_alarm.c:41:24: error:
      'CONFIG_ARCH_INTEL64_HPET_ALARM_CHAN' undeclared

ARCH_INTEL64_HPET_ALARM_CHAN lives inside "if INTEL64_HPET" and nothing
selects INTEL64_HPET.  Enabling that by hand moves the failure to link time,
because intel64_oneshot_lower.c is built only when INTEL64_ONESHOT is set:

  undefined reference to `oneshot_initialize'

Enabling INTEL64_ONESHOT as well finally reaches the real problem.
intel64_oneshot_lower.c implements the counter flavour of struct
oneshot_operations_s, which exists only with ONESHOT_COUNT:

  intel64_oneshot_lower.c: error: 'const struct oneshot_operations_s' has no
      member named 'start_absolute'
  intel64_oneshot_lower.c: error: implicit declaration of function
      'oneshot_count_init'
  intel64_oneshot_lower.c: error: initialization of
      'int (*)(struct oneshot_lowerhalf_s *, const struct timespec *)' from
      incompatible pointer type ... (four more of these)

ONESHOT, ONESHOT_COUNT and ONESHOT_FAST_DIVISION were selected by
ARCH_INTEL64_TSC_DEADLINE and by nothing else, so the other members of the
same choice could never be built.

Select the four from ARCH_INTEL64_HPET_ALARM as well.  INTEL64_ONESHOT
selects INTEL64_HPET in turn, which is what brings
ARCH_INTEL64_HPET_ALARM_CHAN into existence, so one added select closes all
three stages.

Impact: build only, and only for a configuration that could not be built
before.  No existing defconfig selects ARCH_INTEL64_HPET_ALARM.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>

arch/x86_64/src/intel64/Kconfig

@@ -70,6 +70,10 @@ config ARCH_INTEL64_TSC
 
 config ARCH_INTEL64_HPET_ALARM
 	bool "HPET timer alarm support"
+	select INTEL64_ONESHOT
+	select ONESHOT
+	select ONESHOT_COUNT
+	select ONESHOT_FAST_DIVISION
 	select ALARM_ARCH
 	---help---
 		With this option you can enable ALARM_ARCH features that works on top of