Soong: Update documentation on prebuilt* modules.

The prebuilt_etc_host is missing synopsis. Also, cleaned up the
synopsis of the remaining prebuilt* module to be clearer.

Bug: b/128337482
Test: Built the documentation and verified that the output is correct.
Change-Id: I64593970a44b548ac841de79aa0e4aa1699c6c9b
diff --git a/android/prebuilt_etc.go b/android/prebuilt_etc.go
index 6c8fb31..0c68b0c 100644
--- a/android/prebuilt_etc.go
+++ b/android/prebuilt_etc.go
@@ -174,7 +174,8 @@
 	p.AddProperties(&p.properties)
 }
 
-// prebuilt_etc is for prebuilts that will be installed to <partition>/etc/<subdir>
+// prebuilt_etc is for a prebuilt artifact that is installed in
+// <partition>/etc/<sub_dir> directory.
 func PrebuiltEtcFactory() Module {
 	module := &PrebuiltEtc{installDirBase: "etc"}
 	InitPrebuiltEtcModule(module)
@@ -183,6 +184,8 @@
 	return module
 }
 
+// prebuilt_etc_host is for a host prebuilt artifact that is installed in
+// $(HOST_OUT)/etc/<sub_dir> directory.
 func PrebuiltEtcHostFactory() Module {
 	module := &PrebuiltEtc{installDirBase: "etc"}
 	InitPrebuiltEtcModule(module)
@@ -191,7 +194,8 @@
 	return module
 }
 
-// prebuilt_usr_share is for prebuilts that will be installed to <partition>/usr/share/<subdir>
+// prebuilt_usr_share is for a prebuilt artifact that is installed in
+// <partition>/usr/share/<sub_dir> directory.
 func PrebuiltUserShareFactory() Module {
 	module := &PrebuiltEtc{installDirBase: "usr/share"}
 	InitPrebuiltEtcModule(module)
@@ -200,7 +204,8 @@
 	return module
 }
 
-// prebuild_usr_share_host is for host prebuilts that will be installed to <partition>/usr/share/<subdir>
+// prebuild_usr_share_host is for a host prebuilt artifact that is installed in
+// $(HOST_OUT)/usr/share/<sub_dir> directory.
 func PrebuiltUserShareHostFactory() Module {
 	module := &PrebuiltEtc{installDirBase: "usr/share"}
 	InitPrebuiltEtcModule(module)