[otbn,dv] Make otbn_base_vseq::saved_tl_cfg_t unpacked

This won't really matter, but the unnecessary "packed" shows that I
didn't really understand the difference between packed and unpacked
structs in SystemVerilog when I wrote the code in 2022. Or indeed
yesterday morning...

Signed-off-by: Rupert Swarbrick <[email protected]>

Author: rswarbrick

hw/ip/otbn/dv/uvm/env/seq_lib/otbn_base_vseq.sv

@@ -36,7 +36,7 @@ class otbn_base_vseq extends cip_base_vseq #(
   protected int unsigned stop_tokens = 0;
 
   // Saved TL agent configuration
-  typedef struct packed {
+  typedef struct {
     bit          valid;
     int unsigned a_valid_delay_min;
     int unsigned a_valid_delay_max;