Fix issue in encoding CSN_RECURSIVE_ARRAY

The remaining_bits_len is correctly decremented while encoding
CSN_RECURSIVE_ARRAY for fixing the bug.
Details of the bug is in https://projects.osmocom.org/issues/1641

During introduction of basic EGPRS feature new hex dump message
PUASS, from a different working network log was used in Unit test.
It exposed the issue of incorrect handling of recursive array
encoding in osmo-pcu.

Fixes: OS#1641
diff --git a/tests/rlcmac/RLCMACTest.cpp b/tests/rlcmac/RLCMACTest.cpp
index 26d35ec..466b89e 100644
--- a/tests/rlcmac/RLCMACTest.cpp
+++ b/tests/rlcmac/RLCMACTest.cpp
@@ -93,6 +93,7 @@
 	"47240c00400000000000000079eb2ac9402b2b2b2b2b2b", // Packet Uplink Ack Nack
 	"47283c367513ba333004242b2b2b2b2b2b2b2b2b2b2b2b", // Packet Uplink Assignment
 	"400820001a3904df0680efb3300b2b2b2b2b2b2b2b2b2b", // Packet Downlink Assignment (EGPRS)
+	"40284f0000001009810c826f4406809dcecb2b2b2b2b2b", // Packet Uplink Assignment (EGPRS)
 	"4024030f2f0000000087b0042b2b2b2b2b2b2b2b2b2b2b"  // Packet Uplink Ack Nack (EGPRS)
 	"4913e00850884013a8048b2b2b2b2b2b2b2b2b2b2b2b2b"
 	"412430007fffffffffffffffefd19c7ba12b2b2b2b2b2b"