UBUNTU: SAUCE: tty: vt: Fix soft lockup in fbcon cursor blink timer.

BugLink: http://bugs.launchpad.net/bugs/1574814

We are getting somewhat random soft lockups with this signature:

[   86.992215] [<fffffc00080935e0>] el1_irq+0xa0/0x10c
[   86.997082] [<fffffc000841822c>] cursor_timer_handler+0x30/0x54
[   87.002991] [<fffffc000810ec44>] call_timer_fn+0x54/0x1a8
[   87.008378] [<fffffc000810ef88>] run_timer_softirq+0x1c4/0x2bc
[   87.014200] [<fffffc000809077c>] __do_softirq+0x114/0x344
[   87.019590] [<fffffc00080af45c>] irq_exit+0x74/0x98
[   87.024458] [<fffffc00080fac20>] __handle_domain_irq+0x98/0xfc
[   87.030278] [<fffffc000809056c>] gic_handle_irq+0x94/0x190

This is caused by the vt visual_init() function calling into
fbcon_init() with a vc_cur_blink_ms value of zero.  This is a
transient condition, as it is later set to a non-zero value.  But, if
the timer happens to expire while the blink rate is zero, it goes into
an endless loop, and we get soft lockup.

The fix is to initialize vc_cur_blink_ms before calling the con_init()
function.
Tested-by: Ming Lei <ming.lei@canonical.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Scot Doyle <lkml14@scotdoyle.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: stable@vger.kernel.org
Reference: https://lkml.org/lkml/2016/5/17/455
Cc: Ming Lei <ming.lei@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/tty/vt/vt.c

@@ -761,6 +761,7 @@ static void visual_init(struct vc_data *vc, int num, int init)
 	vc->vc_complement_mask = 0;
 	vc->vc_can_do_color = 0;
 	vc->vc_panic_force_write = false;
+	vc->vc_cur_blink_ms = DEFAULT_CURSOR_BLINK_MS;
 	vc->vc_sw->con_init(vc, init);
 	if (!vc->vc_complement_mask)
 		vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;