staging: sm750fb: avoid conflicting vesafb

If vesafb is enabled in the config then /dev/fb0 is created by vesa
and this sm750 driver gets fb1, fb2. But we need to be fb0 and fb1 to
effectively work with xorg.
So if it has been alloted fb1, then try to remove the other fb0.

In the previous send, why #ifdef is used was asked.
https://lkml.org/lkml/2017/6/25/57

Answered at: https://lkml.org/lkml/2017/6/25/69
Also pasting here for reference.

'Did a quick research into "why".
The patch d8801e4d ("x86/PCI: Set IORESOURCE_ROM_SHADOW only for the
default VGA device") has started setting IORESOURCE_ROM_SHADOW in flags
for a default VGA device and that is being done only for x86.
And so, we will need that #ifdef to check IORESOURCE_ROM_SHADOW as that
needs to be checked only for a x86 and not for other arch.'

Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Teddy Wang <teddy.wang@siliconmotion.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/sm750fb/sm750.c

@@ -1053,6 +1053,26 @@ static int sm750fb_frambuffer_alloc(struct sm750_dev *sm750_dev, int fbidx)
 	return err;
 }
 
+static int lynxfb_kick_out_firmware_fb(struct pci_dev *pdev)
+{
+	struct apertures_struct *ap;
+	bool primary = false;
+
+	ap = alloc_apertures(1);
+	if (!ap)
+		return -ENOMEM;
+
+	ap->ranges[0].base = pci_resource_start(pdev, 0);
+	ap->ranges[0].size = pci_resource_len(pdev, 0);
+#ifdef CONFIG_X86
+	primary = pdev->resource[PCI_ROM_RESOURCE].flags &
+					IORESOURCE_ROM_SHADOW;
+#endif
+	remove_conflicting_framebuffers(ap, "sm750_fb1", primary);
+	kfree(ap);
+	return 0;
+}
+
 static int lynxfb_pci_probe(struct pci_dev *pdev,
 			    const struct pci_device_id *ent)
 {
@@ -1061,6 +1081,10 @@ static int lynxfb_pci_probe(struct pci_dev *pdev,
 	int fbidx;
 	int err;
 
+	err = lynxfb_kick_out_firmware_fb(pdev);
+	if (err)
+		return err;
+
 	/* enable device */
 	err = pcim_enable_device(pdev);
 	if (err)