init: moving get_block_device_symlinks() to public API

This is required for init to get by-name symlinks in the first stage
mount with AVB.

Bug: 37552224
Test: first stage mount /vendor with vboot 2.0 (AVB)
Change-Id: Ib067753f651ecea4d4d26215da9294f1c607d95e
Merged-In: Ia0f290542eb1cffce5ae876dfedb453dde960253
diff --git a/init/devices.cpp b/init/devices.cpp
index 405f92e..39571ac 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -526,8 +526,7 @@
     return NULL;
 }
 
-static char **get_block_device_symlinks(struct uevent *uevent)
-{
+char** get_block_device_symlinks(struct uevent* uevent) {
     const char *device;
     struct platform_node *pdev;
     const char *slash;