NetworkPkg/TlsDxe: clean up byte order conversion for EfiTlsCipherList

NetworkPkg/TlsDxe: clean up byte order conversion for EfiTlsCipherList

Fix the following style issues:

- "Data" is accessed through a pointer to UINT16 rather than to a pointer
  to EFI_TLS_CIPHER. While technically correct, UINT16 is harder to
  interpret against the UEFI spec.

- Array subscripting is written with weird *(Pointer + Offset)
  expressions, rather than with Pointer[Offset].

- The byte order is converted with HTONS(), while it should be NTOHS().
  Either way, use the Data1 and Data2 fields of EFI_TLS_CIPHER instead.

Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=915
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Long Qin <qin.long@intel.com>
Reviewed-by: Jiaxin Wu <jiaxin.wu@intel.com>