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.h b/init/devices.h
index 26a064b..3f2cde4 100644
--- a/init/devices.h
+++ b/init/devices.h
@@ -55,4 +55,6 @@
                          unsigned short wildcard);
 int get_device_fd();
 
+char** get_block_device_symlinks(struct uevent* uevent);
+
 #endif	/* _INIT_DEVICES_H */