hw/isa/Kconfig: Fix missing dependency ISA_SUPERIO -> FDC

isa_superio_realize() calls isa_fdc_init_drives(), which is defined
in hw/block/fdc.c, so ISA_SUPERIO needs to select the FDC symbol.

Reported-by: John Snow <jsnow@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210614193220.2007159-2-philmd@redhat.com
Fixes: c0ff379 ("Introduce a CONFIG_ISA_SUPERIO switch for isa-superio.c")
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>

hw/isa/Kconfig

@@ -17,6 +17,7 @@ config ISA_SUPERIO
     bool
     select ISA_BUS
     select PCKBD
+    select FDC
 
 config PC87312
     bool