drm/amd/amdgpu : Remove unused variable

Remove unused variable 'ret', and directly return 0.

Reviewed-by: Junwei Zhang <[e-mail]>
Signed-off-by: Muhammad Falak R Wani <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/cz_ih.c

···
  */
 static int cz_ih_irq_init(struct amdgpu_device *adev)
 {
-	int ret = 0;
 	int rb_bufsz;
 	u32 interrupt_cntl, ih_cntl, ih_rb_cntl;
 	u64 wptr_off;
···
 	/* enable interrupts */
 	cz_ih_enable_interrupts(adev);
 
-	return ret;
+	return 0;
 }
 
 /**