drm: Plumb modifiers through plane init

This is the plumbing for supporting fb modifiers on planes. Modifiers
have already been introduced to some extent, but this series will extend
this to allow querying modifiers per plane. Based on this, the client to
enable optimal modifications for framebuffers.

This patch simply allows the DRM drivers to initialize their list of
supported modifiers upon initializing the plane.

v2: A minor addition from Daniel

v3:
* Updated commit message
* s/INVALID/DRM_FORMAT_MOD_INVALID (Liviu)
* Remove some excess newlines (Liviu)
* Update comment for > 64 modifiers (Liviu)

v4: Minor comment adjustments (Liviu)

v5: Some new platforms added due to rebase

v6: Add some missed plane inits (or maybe they're new - who knows at
this point) (Daniel)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Daniel Stone <daniels@collabora.com> (v2)
Reviewed-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Daniel Stone <daniels@collabora.com>

include/uapi/drm/drm_fourcc.h

@@ -185,6 +185,8 @@ extern "C" {
 #define DRM_FORMAT_MOD_VENDOR_BROADCOM 0x07
 /* add more to the end as needed */
 
+#define DRM_FORMAT_RESERVED	      ((1ULL << 56) - 1)
+
 #define fourcc_mod_code(vendor, val) \
 	((((__u64)DRM_FORMAT_MOD_VENDOR_## vendor) << 56) | (val & 0x00ffffffffffffffULL))
 
@@ -196,6 +198,15 @@ extern "C" {
  * authoritative source for all of these.
  */
 
+/*
+ * Invalid Modifier
+ *
+ * This modifier can be used as a sentinel to terminate the format modifiers
+ * list, or to initialize a variable with an invalid modifier. It might also be
+ * used to report an error back to userspace for certain APIs.
+ */
+#define DRM_FORMAT_MOD_INVALID	fourcc_mod_code(NONE, DRM_FORMAT_RESERVED)
+
 /*
  * Linear Layout
  *