[POWERPC] Make the hvc_console output buffer size settable

So the iSeries console will be faster since it can send up to 200 bytes at
a time to the Hypervisor.  This only affects the tty part of the console,
the console writes are still in 16 byte lots.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

drivers/char/hvc_rtas.c

@@ -94,7 +94,7 @@ static int hvc_rtas_init(void)
 
 	/* Allocate an hvc_struct for the console device we instantiated
 	 * earlier.  Save off hp so that we can return it on exit */
-	hp = hvc_alloc(hvc_rtas_cookie, NO_IRQ, &hvc_rtas_get_put_ops);
+	hp = hvc_alloc(hvc_rtas_cookie, NO_IRQ, &hvc_rtas_get_put_ops, 16);
 	if (IS_ERR(hp))
 		return PTR_ERR(hp);