libertas: make lbs_cmd() usage nicer

Define a macro that relieves the caller from having to use sizeof on
the command structure when calling lbs_cmd(), and move the prototype
of __lbs_cmd() to a new cmd.h file.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/libertas/if_usb.c b/drivers/net/wireless/libertas/if_usb.c
index 1c23166..8ff57a6 100644
--- a/drivers/net/wireless/libertas/if_usb.c
+++ b/drivers/net/wireless/libertas/if_usb.c
@@ -13,6 +13,7 @@
 #include "decl.h"
 #include "defs.h"
 #include "dev.h"
+#include "cmd.h"
 #include "if_usb.h"
 
 #define MESSAGE_HEADER_LEN	4
@@ -108,7 +109,7 @@
 	b2_cmd.action = 0;
 	b2_cmd.version = priv->boot2_version;
 
-	if (lbs_cmd(priv, CMD_SET_BOOT2_VER, &b2_cmd, sizeof(b2_cmd), NULL, 0))
+	if (lbs_cmd(priv, CMD_SET_BOOT2_VER, b2_cmd, NULL, 0))
 		lbs_deb_usb("Setting boot2 version failed\n");
 }