Compiler attributes __packed and __aligned, and DECLARE_FLEX_ARRAY() are
currently used in arch/x86/virt/vmx/tdx/tdx.h, but the relevant headers
are not included explicitly.
There's no build issue in the current code since this "tdx.h" is only
included by arch/x86/virt/vmx/tdx/tdx.c and it includes bunch of other
<linux/xxx.h> before including "tdx.h". But for the better explicitly
include the relevant headers to "tdx.h". Also include <linux/types.h>
for basic variable types like u16.
Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>