Staging: rtl8192e: Fix Sparse Warning of restricted __le16 degrades to integer in rtllib_tx.c

This patch fixes the following sparse warning in rtllib_tx.c-
warning: restricted __le16 degrades to integer

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>