Autogenerate a system_dlkm android_filesystem

This .img file will package the .ko files returned by
`BOARD_SYSTEM_KERNEL_MODULES` (plus some other files). The .ko files
will be clustered by directory, and a `prebuilt_kernel_modules` will
be automatically created for each cluster. These will then be added to
the deps of the top-level system_dlkm android_filesystem.

Bug: 376726109
Test: m out/soong/.intermediates/build/soong/fsgen/soong_filesystem_creator/android_common/diff_test_aosp_cf_x86_64_phone_generated_system_dlkm_image.txt
KATI only installed file(s):
  etc/NOTICE.xml.gz
  etc/build.prop
  etc/fs_config_dirs
  etc/fs_config_files

Change-Id: I96669ad9595379c4de4c67331fc56bfa8d93e036
diff --git a/kernel/prebuilt_kernel_modules.go b/kernel/prebuilt_kernel_modules.go
index e200ee2..4c0a911 100644
--- a/kernel/prebuilt_kernel_modules.go
+++ b/kernel/prebuilt_kernel_modules.go
@@ -32,7 +32,7 @@
 }
 
 func registerKernelBuildComponents(ctx android.RegistrationContext) {
-	ctx.RegisterModuleType("prebuilt_kernel_modules", prebuiltKernelModulesFactory)
+	ctx.RegisterModuleType("prebuilt_kernel_modules", PrebuiltKernelModulesFactory)
 }
 
 type prebuiltKernelModules struct {
@@ -58,7 +58,7 @@
 // prebuilt_kernel_modules installs a set of prebuilt kernel module files to the correct directory.
 // In addition, this module builds modules.load, modules.dep, modules.softdep and modules.alias
 // using depmod and installs them as well.
-func prebuiltKernelModulesFactory() android.Module {
+func PrebuiltKernelModulesFactory() android.Module {
 	module := &prebuiltKernelModules{}
 	module.AddProperties(&module.properties)
 	android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibFirst)