libertas: support boot commands to write persistent firmware and bootloader

Add locking and non-locking versions of if_usb_prog_firmware to support
programming firmware after and before driver bring-up respectively.  Add more
suitable error codes for firmware programming process.  Add capability checks
for persistent features before attempting to use them.

Based on patches from Brajesh Dave and Priyank Singh.

Signed-off-by: Brian Cavagnolo <brian@cozybit.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/if_usb.h

@@ -30,6 +30,7 @@ struct bootcmd
 
 #define BOOT_CMD_RESP_OK		0x0001
 #define BOOT_CMD_RESP_FAIL		0x0000
+#define BOOT_CMD_RESP_NOT_SUPPORTED	0x0002
 
 struct bootcmdresp
 {
@@ -50,6 +51,10 @@ struct if_usb_card {
 	uint8_t ep_in;
 	uint8_t ep_out;
 
+	/* bootcmdresp == 0 means command is pending
+	 * bootcmdresp < 0 means error
+	 * bootcmdresp > 0 is a BOOT_CMD_RESP_* from firmware
+	 */
 	int8_t bootcmdresp;
 
 	int ep_in_size;