do not try an adapter more than once if there are failures

Reference: /n/atom/patch/applied/igbeonce
Date: Mon Apr  7 22:52:36 CES 2014
Signed-off-by: quanstro@quanstr.net

--- /sys/src/nix/k10/etherigbe.c	Mon Apr  7 22:52:36 2014
+++ /sys/src/nix/k10/etherigbe.c	Mon Apr  7 22:52:36 2014
@@ -1935,8 +1935,7 @@
 	Ctlr *ctlr;
 	void *mem;
 
-	p = nil;
-	while(p = pcimatch(p, 0, 0)){
+	for(p = nil; p = pcimatch(p, 0, 0); ){
 		if(p->ccrb != 0x02 || p->ccru != 0)
 			continue;
 
@@ -1974,9 +1973,10 @@
 			break;
 		case 0x00:
 		case 0xFF:
-			print("igbe: unusable CLS; using 32 bytes\n");
-			pcicfgw8(p, PciCLS, 32/4);
-			continue;
+			print("igbe: resetting CLS %d->%d bytes\n", cls*4, 32);
+			cls = 32/4;
+			pcicfgw8(p, PciCLS, cls);
+			break;
 		case 0x08:
 		case 0x10:
 			break;
@@ -2011,9 +2011,12 @@
 igbepnp(Ether* edev)
 {
 	Ctlr *ctlr;
+	static int once;
 
-	if(igbectlrhead == nil)
+	if(once == 0){
+		once = 1;
 		igbepci();
+	}
 
 	/*
 	 * Any adapter matches if no edev->port is supplied,