x86/mm/pat, drivers/media/ivtv: Move the PAT warning and replace WARN() with pr_warn()

On built-in kernels this warning will always splat, even if no ivtvfb
hardware is present, as this is part of the module init:

	if (WARN(pat_enabled(),
		 "ivtvfb needs PAT disabled, boot with nopat kernel parameter\n")) {

Fix that by shifting the PAT requirement check out under the code
that does the "quasi-probe" for the device.

This device driver relies on an existing driver to find its own devices,
it looks for that device driver and its own found devices, then uses
driver_for_each_device() to try to see if it can probe each of those
devices as a frambuffer device with ivtvfb_init_card().

We tuck the PAT requiremenet check then on the ivtvfb_init_card() call
making the check at least require an ivtv device present before
complaining.

Reported-by: Fengguang Wu <fengguang.wu@intel.com> [0-day test robot]
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andy@silverblocksystems.net
Cc: benh@kernel.crashing.org
Cc: bp@suse.de
Cc: dan.j.williams@intel.com
Cc: dledford@redhat.com
Cc: jkosina@suse.cz
Cc: julia.lawall@lip6.fr
Cc: luto@amacapital.net
Cc: mchehab@osg.samsung.com
Link: http://lkml.kernel.org/r/1437167245-28273-3-git-send-email-mcgrof@do-not-panic.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/media/pci/ivtv/ivtvfb.c

@@ -38,6 +38,8 @@
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/fb.h>
@@ -1171,6 +1173,13 @@ static int ivtvfb_init_card(struct ivtv *itv)
 {
 	int rc;
 
+#ifdef CONFIG_X86_64
+	if (pat_enabled()) {
+		pr_warn("ivtvfb needs PAT disabled, boot with nopat kernel parameter\n");
+		return -ENODEV;
+	}
+#endif
+
 	if (itv->osd_info) {
 		IVTVFB_ERR("Card %d already initialised\n", ivtvfb_card_id);
 		return -EBUSY;
@@ -1265,12 +1274,6 @@ static int __init ivtvfb_init(void)
 	int registered = 0;
 	int err;
 
-#ifdef CONFIG_X86_64
-	if (WARN(pat_enabled(),
-		 "ivtvfb needs PAT disabled, boot with nopat kernel parameter\n")) {
-		return -ENODEV;
-	}
-#endif
 
 	if (ivtvfb_card_id < -1 || ivtvfb_card_id >= IVTV_MAX_CARDS) {
 		printk(KERN_ERR "ivtvfb:  ivtvfb_card_id parameter is out of range (valid range: -1 - %d)\n",