drm/v3d: Delete v3d_dev->pdev

We already have it in v3d_dev->drm.dev with zero additional pointer
chasing. Personally I don't like duplicated pointers like this
because:
- reviewers need to check whether the pointer is for the same or
different objects if there's multiple
- compilers have an easier time too

To avoid having to pull in some big headers I implemented the casting
function as a macro instead of a static inline. Typechecking thanks to
container_of still assured.

But also a bit a bikeshed, so feel free to ignore.

v2: More parens for v3d_to_pdev macro (checkpatch)

Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415074034.175360-11-daniel.vetter@ffwll.ch

drivers/gpu/drm/v3d/v3d_drv.c

@@ -235,7 +235,7 @@ static int
 map_regs(struct v3d_dev *v3d, void __iomem **regs, const char *name)
 {
 	struct resource *res =
-		platform_get_resource_byname(v3d->pdev, IORESOURCE_MEM, name);
+		platform_get_resource_byname(v3d_to_pdev(v3d), IORESOURCE_MEM, name);
 
 	*regs = devm_ioremap_resource(v3d->drm.dev, res);
 	return PTR_ERR_OR_ZERO(*regs);
@@ -255,7 +255,6 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
 	if (IS_ERR(v3d))
 		return PTR_ERR(v3d);
 
-	v3d->pdev = pdev;
 	drm = &v3d->drm;
 
 	platform_set_drvdata(pdev, drm);