gsm_7bit_encode_n(): fix integer overflow in gsm_septets2octets()

Using 'uint8_t' for the length argument is definitely a bad idea.
Because of this, packing more than 255 septets would not work as
expected.  Deprecate the old function and use 'size_t' instead.

Change-Id: Ib1aac538afeb0a5c76a1df472d555139a496e12e
diff --git a/tests/sms/sms_test.c b/tests/sms/sms_test.c
index c7f47e2..3e14529 100644
--- a/tests/sms/sms_test.c
+++ b/tests/sms/sms_test.c
@@ -384,7 +384,7 @@
 	memcpy(tmp, septet_data, concatenated_part1_septet_length);
 
 	/* In our case: test_multiple_decode[0].ud_hdr_ind equals number of padding bits*/
-	octet_length = gsm_septets2octets(coded, tmp, concatenated_part1_septet_length, test_multiple_encode[0].ud_hdr_ind);
+	octet_length = gsm_septet_pack(coded, tmp, concatenated_part1_septet_length, test_multiple_encode[0].ud_hdr_ind);
 
 	/* copy header */
 	memset(tmp, 0x42, sizeof(tmp));
@@ -402,7 +402,7 @@
 	memcpy(tmp, septet_data + concatenated_part1_septet_length, concatenated_part2_septet_length);
 
 	/* In our case: test_multiple_decode[1].ud_hdr_ind equals number of padding bits*/
-	octet_length = gsm_septets2octets(coded, tmp, concatenated_part2_septet_length, test_multiple_encode[1].ud_hdr_ind);
+	octet_length = gsm_septet_pack(coded, tmp, concatenated_part2_septet_length, test_multiple_encode[1].ud_hdr_ind);
 
 	/* copy header */
 	memset(tmp, 0x42, sizeof(tmp));