[SPARC64]: Add hypervisor API negotiation and fix console bugs.

Hypervisor interfaces need to be negotiated in order to use
some API calls reliably.  So add a small set of interfaces
to request API versions and query current settings.

This allows us to fix some bugs in the hypervisor console:

1) If we can negotiate API group CORE of at least major 1
   minor 1 we can use con_read and con_write which can improve
   console performance quite a bit.

2) When we do a console write request, we should hold the
   spinlock around the whole request, not a byte at a time.
   What would happen is that it's easy for output from
   different cpus to get mixed with each other.

3) Use consistent udelay() based polling, udelay(1) each
   loop with a limit of 1000 polls to handle stuck hypervisor
   console.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/setup.c

@@ -269,6 +269,7 @@ void __init per_cpu_patch(void)
 
 void __init sun4v_patch(void)
 {
+	extern void sun4v_hvapi_init(void);
 	struct sun4v_1insn_patch_entry *p1;
 	struct sun4v_2insn_patch_entry *p2;
 
@@ -300,6 +301,8 @@ void __init sun4v_patch(void)
 
 		p2++;
 	}
+
+	sun4v_hvapi_init();
 }
 
 #ifdef CONFIG_SMP