Remove fixed limit on number of guests, and lguests array.

Back when we had all the Guest state in the switcher, we had a fixed
array of them.  This is no longer necessary.

If we switch the network code to using random_ether_addr (46 bits is
enough to avoid clashes), we can get rid of the concept of "guest id"
altogether.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/lguest.h

@@ -41,8 +41,6 @@ struct lguest_data
 /* Fields initialized by the Host at boot: */
 	/* Memory not to try to access */
 	unsigned long reserve_mem;
-	/* ID of this Guest (used by network driver to set ethernet address) */
-	u16 guestid;
 	/* KHz for the TSC clock. */
 	u32 tsc_khz;