Allow correct interpretation of BOOT_TARGET.

Change 2/2 to allow hnvram to properly read
BOOT_TARGET. This specifies the interpretation
of BOOT_TARGET.

Change-Id: Ia034493f23a7b528e7bfedb07dbcc98bb895c594
(cherry picked from commit 39035657101699fcf59c68b35a7944ea8a76867c)
diff --git a/hnvram/hnvram_main.c b/hnvram/hnvram_main.c
index b850048..323d62e 100644
--- a/hnvram/hnvram_main.c
+++ b/hnvram/hnvram_main.c
@@ -83,6 +83,7 @@
   {"LASER_CHANNEL",        NVRAM_FIELD_LASER_CHANNEL,     HNVRAM_STRING},
   {"MAC_ADDR_PON",         NVRAM_FIELD_MAC_ADDR_PON,      HNVRAM_MAC},
   {"PRODUCTION_UNIT",      NVRAM_FIELD_PRODUCTION_UNIT,   HNVRAM_STRING},
+  {"BOOT_TARGET",          NVRAM_FIELD_BOOT_TARGET,       HNVRAM_STRING},
 };
 
 const hnvram_field_t* get_nvram_field(const char* name) {