Remove unnecessary kernel modules

... for memory efficiency and better security

Bug: 217752858
Test: run microdroid
Compare `cat /proc/meminfo  | grep MemFree` before and after this change
131800 kB -> 133668 kb (x86_64)
141312 kb -> 145656 kb (arm64)

Change-Id: Iea13ca857aa007b8331372b828692e38e8196b7f
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 7384cef..a93a801 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -292,18 +292,24 @@
     avb_private_key: ":microdroid_sign_key",
 }
 
-android_filesystem {
-    name: "microdroid_vendor_ramdisk-5.10",
+prebuilt_kernel_modules {
+    name: "microdroid_kernel_modules",
     arch: {
         arm64: {
-            deps: ["virt_device_prebuilts_kernel_modules-5.10-arm64"],
+            srcs: [":virt_device_prebuilts_kernel_modules_microdroid-5.10-arm64"],
         },
         x86_64: {
-            deps: ["virt_device_prebuilts_kernel_modules-5.10-x86_64"],
+            srcs: [":virt_device_prebuilts_kernel_modules_microdroid-5.10-x86_64"],
         },
     },
+    kernel_version: "5.10",
+}
+
+android_filesystem {
+    name: "microdroid_vendor_ramdisk-5.10",
     deps: [
         "microdroid_fstab",
+        "microdroid_kernel_modules",
     ],
     base_dir: "first_stage_ramdisk",
     type: "compressed_cpio",