Add thread_mode and DPDK EAL options to config.ini

Document thread_mode (native-mt), memory, no_huge, file_prefix as
commented defaults so users know they exist.

Author: jfb8856606

config.ini

@@ -2,9 +2,19 @@
 # Hexadecimal bitmask of cores to run on.
 lcore_mask=1
 
+# Thread mode: 0=multi-process (default), 1=single-process multi-thread.
+# In thread_mode=1, all lcores in lcore_mask run as threads in one process,
+# each with its own vnet stack instance. nb_threads = lcore_mask set-bit count.
+#thread_mode=0
+
 # Number of memory channels.
 channel=4
 
+# DPDK EAL options (all optional, commented = use DPDK defaults).
+#memory=1024
+#no_huge=0
+#file_prefix=dpdk
+
 # Specify base virtual address to map.
 #base_virtaddr=0x7f0000000000