HACK media: qcom: camss: fix VFE pm domain off

Fix NULL pointer check before device_link_del
is called.

Unable to handle kernel NULL pointer dereference at virtual address 000000000000032c
Call trace:
 device_link_put_kref+0xc/0xb8
 device_link_del+0x30/0x48
 vfe_pm_domain_off+0x24/0x38 [qcom_camss]
 vfe_put+0x9c/0xd0 [qcom_camss]
 vfe_set_power+0x48/0x58 [qcom_camss]
 pipeline_pm_power_one+0x154/0x158 [videodev]
 pipeline_pm_power+0x74/0xfc [videodev]
 v4l2_pipeline_pm_use+0x54/0x90 [videodev]
 v4l2_pipeline_pm_put+0x14/0x34 [videodev]
 video_release+0x2c/0x44 [qcom_camss]
 v4l2_release+0xe4/0xec [videodev]

Fixes: eb73fac ("media: qcom: camss: Use common VFE pm_domain_on/pm_domain_off where applicable")
Tested-by: Yassine Oudjana <y.oudjana@protonmail.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>

Author: barni2000

drivers/media/platform/qcom/camss/camss-vfe.c

@@ -596,7 +596,7 @@ void vfe_isr_reset_ack(struct vfe_device *vfe)
  */
 void vfe_pm_domain_off(struct vfe_device *vfe)
 {
-	if (!vfe->genpd)
+	if (!vfe->genpd_link)
 		return;
 
 	device_link_del(vfe->genpd_link);