Build ramdisk with soong

This is the first step to build the ramdisk, it still has some diffs
with with the make-generated ramdisk though.

Bug: 378146476
Test: m soong_generated_ramdisk_filesystem_test
Change-Id: I767ea9d09e4d6413c2ec5af3120595e2001c9bb7
diff --git a/android/module.go b/android/module.go
index 58ae885..3b30c11 100644
--- a/android/module.go
+++ b/android/module.go
@@ -1382,6 +1382,8 @@
 		if config.SystemExtPath() == "system_ext" {
 			partition = "system_ext"
 		}
+	} else if m.InstallInRamdisk() {
+		partition = "ramdisk"
 	}
 	return partition
 }