Minor fixes to make the Xen Dom0 console work. This includes always
returning there's pending input in xencons_has_input, because on Dom0
there's no shared ring and we cannot test the indexes. The second
fix is to use the CONSOLEIO_read hypercall in order to read input
data from the Xen console.
Sponsored by: Citrix Systems R&D
dev/xen/console/xencons_ring.c:
- Always return true in xencons_has_input for Dom0.
- Implement Dom0 console support for xencons_handle_input.