Remove the MTX_SPIN flag to the shared code MUTEX

as it was causing a panic, also took the opportunity
to rename the lock for clarity.

sys/dev/e1000/e1000_osdep.h

@@ -82,8 +82,7 @@
 /* Mutex used in the shared code */
 #define E1000_MUTEX                     struct mtx
 #define E1000_MUTEX_INIT(mutex)         mtx_init((mutex), #mutex, \
-                                        MTX_NETWORK_LOCK, \
-                                        MTX_DEF | MTX_SPIN)
+                                        "E1000 Shared Lock", MTX_DEF)
 #define E1000_MUTEX_DESTROY(mutex)      mtx_destroy(mutex)
 #define E1000_MUTEX_LOCK(mutex)         mtx_lock(mutex)
 #define E1000_MUTEX_TRYLOCK(mutex)      mtx_trylock(mutex)