x86/misc: post cleanup

x86/misc: post cleanup

* panic() now works on early boot.  Replace EARLY_FAIL()
* Cleanup __set_intr_gate() & friends.  The master IDT is fully constructed on
  early boot, and only subsequently altered on the crash path.  Make them
  private to traps.c, move them into .init, and remove the loop over all idts,
  as __set_intr_gate() will never find an AP to patch. (For some reason,
  leaving out the noinline causes ~1.5k of code bloat from GCC inlining
  everything)
* No need to clear X86_EFLAGS_NT in cpu_init().  This is covered by the eflags
  reset in __high_start().
* Missing '\n' from unexpected MCE printk.
* load_system_tables() is x86 specific.  Move its declaration into an x86 header.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>