cosmetic: vlr: rename auth_tuple_max_use_count to _reuse_

The name auth_tuple_max_use_count suggests that if I want to use each auth
tuple exactly once, I need to set it to 1. Curiously, so far you need to set
to intended uses - 1.

Reflect this in its name by renaming to auth_tuple_max_reuse_count.

I first considered to not rename but change the if-conditions so that == 1
means each tuple is used once, and upon struct vlr allocation, set the default
to 1. That would also logically entail that setting to 0 means to re-use
vectors infinitely often, like now a value < 0 does. That means, when
allocating a vlr struct zeroed out, we would by default have the most
dangerous/unsafe configuration. It's no problem to set a default to 1 upon
allocation, but by renaming the variable instead, we get safer alloc-zero
behavior and don't need to change any conditionals in the code (even though the
patch ends up considerably larger from all the renaming).

Change-Id: I0b036cae1536d5d6fb2304f837ed1a6c3713be55
diff --git a/include/osmocom/msc/vlr.h b/include/osmocom/msc/vlr.h
index e9afde3..d5306fa 100644
--- a/include/osmocom/msc/vlr.h
+++ b/include/osmocom/msc/vlr.h
@@ -222,7 +222,7 @@
 		bool retrieve_imeisv_ciphered;
 		bool assign_tmsi;
 		bool check_imei_rqd;
-		int auth_tuple_max_use_count;
+		int auth_tuple_max_reuse_count;
 		bool auth_reuse_old_sets_on_error;
 		bool parq_retrieve_imsi;
 		bool is_ps;