net/fm: call fm_port_to_index() with proper checks

Some of the fm_port_to_index() callers did not check for -1 return value and
used -1 as an array index.

Signed-off-by: Marian Rotariu <marian.rotariu@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

drivers/net/fm/fm.h

@@ -143,6 +143,7 @@ struct fm_eth {
 #define MAX_RXBUF_LOG2		11
 #define MAX_RXBUF_LEN		(1 << MAX_RXBUF_LOG2)
 
-#define PORT_IS_ENABLED(port)	fm_info[fm_port_to_index(port)].enabled
+#define PORT_IS_ENABLED(port)	(fm_port_to_index(port) == -1 ? \
+	0 : fm_info[fm_port_to_index(port)].enabled)
 
 #endif /* __FM_H__ */

drivers/net/fm/init.c

@@ -147,6 +147,9 @@ void fm_disable_port(enum fm_port port)
 {
 	int i = fm_port_to_index(port);
 
+	if (i == -1)
+		return;
+
 	fm_info[i].enabled = 0;
 	fman_disable_port(port);
 }
@@ -155,6 +158,9 @@ void fm_enable_port(enum fm_port port)
 {
 	int i = fm_port_to_index(port);
 
+	if (i == -1)
+		return;
+
 	fm_info[i].enabled = 1;
 	fman_enable_port(port);
 }