minui: Add support for multiple connectors

Add support for multiple connectors.

Bug: 194732653
Test: charging animation can be displayed on different connectors
Change-Id: If9b9eac25ce6e4c582aeb7c52e94ca266f623438
diff --git a/minui/graphics.cpp b/minui/graphics.cpp
index f25694a..597f2ce 100644
--- a/minui/graphics.cpp
+++ b/minui/graphics.cpp
@@ -450,6 +450,10 @@
   gr_backend->Blank(blank);
 }
 
+void gr_fb_blank(bool blank, int index) {
+  gr_backend->Blank(blank, static_cast<MinuiBackend::DrmConnector>(index));
+}
+
 void gr_rotate(GRRotation rot) {
   rotation = rot;
 }