drm/radeon: enable pci bus mastering after card is initialised (v2)

This closes a race seen with kexec where we enable PCI bus mastering
but the card has been reinitialised fully yet.

This was previously fixed by a patch from Jerome, but this should
close the race completely.

v2: add SI support as suggested by Alex.

Reported-and-tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index ac7a199..14919e1 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -3217,6 +3217,8 @@
 	/* force the active interrupt state to all disabled */
 	si_disable_interrupt_state(rdev);
 
+	pci_set_master(rdev->pdev);
+
 	/* enable irqs */
 	si_enable_interrupts(rdev);