minios: move stateful mounting to utils

Move the function that mounts stateful partition to utils. This can be
used by log storage as well.

BUG=b:277753168
TEST=`FEATURES=test emerge-${BOARD}  minios`

Change-Id: Ib33e208411b78598ffaa96806a60d28e8ae3efa7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/4566752
Tested-by: Saketh Pothireddy <[email protected]>
Commit-Queue: Saketh Pothireddy <[email protected]>
Reviewed-by: Jae Hoon Kim <[email protected]>
diff --git a/minios/utils.h b/minios/utils.h
index 426c527..d31196e 100644
--- a/minios/utils.h
+++ b/minios/utils.h
@@ -69,6 +69,8 @@
   return base::StringPrintf("[CoreServicesAlert<%s>] ", category.c_str());
 }
 
+bool MountStatefulPartition(ProcessManagerInterface* process_manager);
+
 }  // namespace minios
 
 #endif  // MINIOS_UTILS_H__