vlr: fix IMEI length

Set the length of vlr_subscr->imei to
	GSM23003_IMEI_NUM_DIGITS_NO_CHK (14)
instead of
	GSM23003_IMEISV_NUM_DIGITS (16).

Note that there is also GSM23003_IMEI_NUM_DIGITS (15), which includes
an additional checksum digit. This digit is not intended for digital
transmission, so we don't need to store it. Also by not storing it, we
can simply copy the IMEI-part from the IMEISV to the IMEI without
worrying about the checksum (will be done in a follow up patch).

A good overview of the IMEI/IMEISV structure is here:
https://en.wikipedia.org/wiki/International_Mobile_Equipment_Identity#Structure_of_the_IMEI_and_IMEISV_(IMEI_software_version)

Related: OS#2542
Change-Id: Iaf2569c099874b55acbd748b776394726cc5ce54
diff --git a/include/osmocom/msc/vlr.h b/include/osmocom/msc/vlr.h
index 4c11951..b1c0d5d 100644
--- a/include/osmocom/msc/vlr.h
+++ b/include/osmocom/msc/vlr.h
@@ -146,7 +146,7 @@
 	struct osmo_cell_global_id cgi;			/* 2.4.16 */
 
 	char imeisv[GSM23003_IMEISV_NUM_DIGITS+1];	/* 2.2.3 */
-	char imei[GSM23003_IMEISV_NUM_DIGITS+1];	/* 2.1.9 */
+	char imei[GSM23003_IMEI_NUM_DIGITS_NO_CHK+1];	/* 2.1.9 */
 	bool imsi_detached_flag;			/* 2.7.1 */
 	bool conf_by_radio_contact_ind;			/* 2.7.4.1 */
 	bool sub_dataconf_by_hlr_ind;			/* 2.7.4.2 */