tile: various console improvements

This change improves and cleans up the tile console.

- We enable HVC_IRQ support on tilegx, with the addition of a new
  Tilera hypervisor API for tilegx to allow a console IPI.  If IPI
  support is not available we fall back to the previous polling mode.

- We simplify the earlyprintk code to use CON_BOOT and eliminate some
  of the other supporting earlyprintk code.

- A new tile_console_write() primitive is used to send output to
  the console and is factored out of the hvc_tile driver.
  This lets us support a "sim_console" boot argument to allow using
  simulator hooks to send output to the "console" as a slightly
  faster alternative to emulating the hardware more directly.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/tile/include/asm/setup.h

@@ -24,9 +24,8 @@
  */
 #define MAXMEM_PFN	PFN_DOWN(MAXMEM)
 
+int tile_console_write(const char *buf, int count);
 void early_panic(const char *fmt, ...);
-void warn_early_printk(void);
-void __init disable_early_printk(void);
 
 /* Init-time routine to do tile-specific per-cpu setup. */
 void setup_cpu(int boot);