libertas: remove two libertas sparse warning

Johannes Berg detected this two sparse warnings:

drivers/net/wireless/libertas/cmd.c:609:16: warning: cast to restricted __le16
drivers/net/wireless/libertas/cmd.c:611:16: warning: cast to restricted __le16

... but cmd.minlevel is "s8", so we can access it directly and hope
for the sign-extension-code in the compiler to convert that to the
"s16" type.
Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/cmd.c

@@ -605,9 +605,9 @@ int lbs_get_tx_power(struct lbs_private *priv, s16 *curlevel, s16 *minlevel,
 	if (ret == 0) {
 		*curlevel = le16_to_cpu(cmd.curlevel);
 		if (minlevel)
-			*minlevel = le16_to_cpu(cmd.minlevel);
+			*minlevel = cmd.minlevel;
 		if (maxlevel)
-			*maxlevel = le16_to_cpu(cmd.maxlevel);
+			*maxlevel = cmd.maxlevel;
 	}
 
 	lbs_deb_leave(LBS_DEB_CMD);