Fix CONFIG_INTERWORKING=y build without CONFIG_HS20=y
Commit 34f28519027d2504168e109519112c1b12d1fdf6 ('MBO: Parse MBO
ANQP-element on STA') started using the type variable outside
CONFIG_HS20 block, but forgot to remove the ifdef from the variable
declaration.
Signed-off-by: Jouni Malinen <j@w1.fi>