Platform/ARM: Add NetworkPkg/NetworkPkg.dec as the package dependency

NetLib will be moved from MdeModulePkg and NetworkPkg.
So, the module that consumes NetLib need to depend on NetworkPkg.dec.

Signed-off-by: Liming Gao <liming.gao@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>