Revert "Remove references to android15-6.1 microdroid kernel"

This reverts commit befa999518814215f9b68f2bafbbb564401743b0.

Reason for revert: Likely culprit for b/352525023  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Change-Id: I58a0eab8cb797fc7ccdf40840d146bba41e8a4f6
diff --git a/microdroid/kernel/Android.bp b/microdroid/kernel/Android.bp
index 7a8af90..5e12d27 100644
--- a/microdroid/kernel/Android.bp
+++ b/microdroid/kernel/Android.bp
@@ -42,6 +42,7 @@
     name: "release_avf_microdroid_kernel_version",
     values: [
         "android14_61",
+        "android15_61",
         "android15_66",
     ],
 }
@@ -54,6 +55,9 @@
             android14_61: {
                 srcs: ["android14-6.1/arm64/kernel-6.1"],
             },
+            android15_61: {
+                srcs: ["android15-6.1/arm64/kernel-6.1"],
+            },
             android15_66: {
                 srcs: ["android15-6.6/arm64/kernel-6.6"],
             },
@@ -76,6 +80,9 @@
             android14_61: {
                 srcs: ["android14-6.1/x86_64/kernel-6.1"],
             },
+            android15_61: {
+                srcs: ["android15-6.1/x86_64/kernel-6.1"],
+            },
             android15_66: {
                 srcs: ["android15-6.6/x86_64/kernel-6.6"],
             },