x86, realmode: Change EFER to a single u64 field

Change EFER to be a single u64 field instead of two u32 fields; change
the order to maintain alignment.  Note that on x86-64 cr4 is really
also a 64-bit quantity, although we can only set the low 32 bits from
the trampoline code since it is still executing in 32-bit mode at that
point.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@intel.com>

arch/x86/include/asm/realmode.h

@@ -35,9 +35,8 @@ struct trampoline_header {
 	u32 gdt_base;
 #else
 	u64 start;
+	u64 efer;
 	u32 cr4;
-	u32 efer_low;
-	u32 efer_high;
 #endif
 };