since panic was changed to a print, add \n and return to
prevent double unlock (or lock discoherence).

Reference: /n/atom/patch/applied2013/adrbadfree
Date: Thu Aug 22 22:40:19 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/adr.c	Thu Aug 22 22:39:46 2013
+++ /sys/src/nix/k10/adr.c	Thu Aug 22 22:39:47 2013
@@ -310,7 +310,8 @@
 	m = adrlook(base, len);
 	if(m == nil || m->use == Mfree){
 		unlock(&adr);
-		print("should panic: bad adrfree %#P %#P", base, len);
+		print("should panic: bad adrfree %#P %#P\n", base, len);
+		return;
 	}
 	m->use = Mfree;
 	m->memflags = 0;