[Ozone] Update GYP and GN to include a DRM platform

ui/ozone/ozone.gni

Index: ui/ozone/ozone.gni
diff --git a/ui/ozone/ozone.gni b/ui/ozone/ozone.gni
index 867813c50af2a6abb70b274ad903a74f19e9ef3e..8556cee2f1f3b100aad8bfbbbcb30299c1a47647 100644
--- a/ui/ozone/ozone.gni
+++ b/ui/ozone/ozone.gni
@@ -14,6 +14,7 @@ declare_args() {
   # Enable individual platforms.
   ozone_platform_caca = false
   ozone_platform_dri = false
+  ozone_platform_drm = false
   ozone_platform_egltest = false
   ozone_platform_gbm = false
   ozone_platform_test = false
@@ -25,6 +26,7 @@ declare_args() {
     # Build all platforms whose deps are in install-build-deps.sh.
     # Only these platforms will be compile tested by buildbots.
     ozone_platform_dri = true
+    ozone_platform_drm = true
     ozone_platform_test = true
     ozone_platform_egltest = true
   }