tools: satisfy shellcheck and drop stale references to the dropped patch

The CI shellcheck step would have failed on three unused variables. Two were
leftovers in probe-cf8-transaction.sh from before the status decoding was
simplified; the third was a loop counter in probe-imc-documented.sh that
nothing reads.

While there: probe-cf8-transaction.sh still described itself in terms of "patch
1/2 of the series", which no longer exists precisely because of what this
script measured. Reworded to say what it establishes and why it is kept.

tools/probe-imc-documented.sh

@@ -73,7 +73,7 @@ probe_one()
 {
 	local bdf=$1 ch=$2
 	local stat=${SMB_STAT[ch]} cmd=${SMB_CMD[ch]} cntl=${SMB_CNTL[ch]}
-	local cntl_val stat_val cmd_saved command i data
+	local cntl_val stat_val cmd_saved command data
 
 	cntl_val=$(read_reg "$bdf" "$cntl")
 	stat_val=$(read_reg "$bdf" "$stat")
@@ -96,7 +96,7 @@ probe_one()
 	printf '  issuing SMBCMD=0x%08x (read SA=%d BA=%s)\n' "$command" "$SA" "$BA"
 	setpci -s "$bdf" "$cmd.L=$(printf '%08x' "$command")"
 
-	for i in $(seq 1 50); do
+	for _ in $(seq 1 50); do
 		stat_val=$(read_reg "$bdf" "$stat")
 		((stat_val & STAT_BUSY)) || break
 		sleep 0.005