[kernel][arch] Move <lib/arch/x86/descriptor.h> out of x86/ sub-library

This header can be used anywhere and by stated policy should not
have been in the x86/ sub-library.  The moved file was also fixed
by `fx format-code`.

Test: no code changes
Change-Id: I85437ffd556352c51745bac09a7d456eceaff0a8
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/403057
Commit-Queue: Joshua Seaton <joshuaseaton@google.com>
Testability-Review: Roland McGrath <mcgrathr@google.com>
Reviewed-by: Joshua Seaton <joshuaseaton@google.com>
diff --git a/zircon/kernel/lib/arch/x86/include/lib/arch/x86/descriptor.h b/zircon/kernel/lib/arch/include/lib/arch/x86/descriptor.h
similarity index 92%
rename from zircon/kernel/lib/arch/x86/include/lib/arch/x86/descriptor.h
rename to zircon/kernel/lib/arch/include/lib/arch/x86/descriptor.h
index 4dff7a0..8027131 100644
--- a/zircon/kernel/lib/arch/x86/include/lib/arch/x86/descriptor.h
+++ b/zircon/kernel/lib/arch/include/lib/arch/x86/descriptor.h
@@ -4,7 +4,8 @@
 // license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT
 
-#pragma once
+#ifndef ZIRCON_KERNEL_LIB_ARCH_INCLUDE_LIB_ARCH_X86_DESCRIPTOR_H_
+#define ZIRCON_KERNEL_LIB_ARCH_INCLUDE_LIB_ARCH_X86_DESCRIPTOR_H_
 
 #include <hwreg/bitfields.h>
 
@@ -107,7 +108,9 @@
   uint32_t base_hi32;
   uint32_t rsvdz;
 
-  constexpr uint64_t base() const { return (static_cast<uint64_t>(base_hi32) << 32) | Desc32::base(); }
+  constexpr uint64_t base() const {
+    return (static_cast<uint64_t>(base_hi32) << 32) | Desc32::base();
+  }
 
   constexpr auto& set_base(uint64_t base) {
     base_hi32 = static_cast<uint32_t>(base >> 32);
@@ -116,3 +119,5 @@
 };
 
 }  // namespace arch
+
+#endif  // ZIRCON_KERNEL_LIB_ARCH_INCLUDE_LIB_ARCH_X86_DESCRIPTOR_H_