pseudo: Fix enum typedef

'pseudo_access_t' is a type, so use typedef.

Fixes building pseudo with gcc 10 where -fno-common is the default.

Signed-off-by: Jacob Kroon <jacob.kroon@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>