usb: usbtest: fix the bit mask of usb 2.0 extension descriptor

USB 2.1 Link PM adds to use bits[1:15] according to USB 2.0 ECN Errata for
Link Power Management spec.

Bit	Encoding
0	Reserved
1	LPM
2	BESL & Altemate HIRD definitions supported
3	Recommended Baseline BESL valid
4	Recommended Deep BESL valid
11:8	Recommended Baseline BESL value
15:12	Recommended Deep BESL value
31:16	Reserved

So fix the bit mask from 0x1e to 0xfffe.

Reported-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/usbtest.c

@@ -619,8 +619,8 @@ static int is_good_ext(struct usbtest_dev *tdev, u8 *buf)
 	}
 
 	attr = le32_to_cpu(ext->bmAttributes);
-	/* bits[1:4] is used and others are reserved */
-	if (attr & ~0x1e) {	/* reserved == 0 */
+	/* bits[1:15] is used and others are reserved */
+	if (attr & ~0xfffe) {	/* reserved == 0 */
 		ERROR(tdev, "reserved bits set\n");
 		return 0;
 	}