staging/easycap: don't mask return value of usb_control_msg() by 0xFF

masking return value of usb_control_msg() will mask negative
error values into positive.

Cc: Mike Thomas <rmthomas@sciolus.org>
Reported-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Reviewed-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/easycap/easycap_low.c

@@ -270,7 +270,7 @@ static int regget(struct usb_device *pusb_device,
 			0x00,
 			index, reg, reg_size, 50000);
 
-	return 0xFF & rc;
+	return rc;
 }
 
 static int regset(struct usb_device *pusb_device, u16 index, u16 value)