genksyms: fix syntax error for builtin (u)int*x*_t types

A longstanding issue with genksyms is that it has hidden syntax errors.

When a syntax error occurs, yyerror() is called. However,
error_with_pos() is a no-op unless the -w option is provided.

You can observe syntax errors by manually passing the -w option.

For example, genksyms fails to parse the following code in
arch/arm64/lib/xor-neon.c:

    static inline uint64x2_t eor3(uint64x2_t p, uint64x2_t q, uint64x2_t r)
    {
            [ snip ]
    }

The syntax error occurs because genksyms does not recognize the
uint64x2_t keyword.

This commit adds support for builtin types described in Arm Neon
Intrinsics Reference.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nicolas Schier <n.schier@avm.de>