staging: r8188eu: fix a memory leak in rtw_wx_read32()

Free "ptmp" before returning -EINVAL.

Fixes: 2b42bd58 ("staging: r8188eu: introduce new os_dep dir for RTL8188eu driver")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20211109114935.GC16587@kiliSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/os_dep/ioctl_linux.c

@@ -1980,6 +1980,7 @@ static int rtw_wx_read32(struct net_device *dev,
 	u32 data32;
 	u32 bytes;
 	u8 *ptmp;
+	int ret;
 
 	padapter = (struct adapter *)rtw_netdev_priv(dev);
 	p = &wrqu->data;
@@ -2007,12 +2008,17 @@ static int rtw_wx_read32(struct net_device *dev,
 		break;
 	default:
 		DBG_88E(KERN_INFO "%s: usage> read [bytes],[address(hex)]\n", __func__);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err_free_ptmp;
 	}
 	DBG_88E(KERN_INFO "%s: addr = 0x%08X data =%s\n", __func__, addr, extra);
 
 	kfree(ptmp);
 	return 0;
+
+err_free_ptmp:
+	kfree(ptmp);
+	return ret;
 }
 
 static int rtw_wx_write32(struct net_device *dev,