UefiPayloadPkg: Fix build error

UefiPayloadPkg: Fix build error

On windows build, need add "-DPLATFORMX64_ENABLE=TRUE" in the build
command line beside -DNETWORK_DRIVER_ENABLE=TRUE in order build
network features. So update DSC to set PLATFORMX64_ENABLE to TRUE
when building network feature.
On Linux build, DSC file should not have PcdAllowHttpConnections
without building network feature, else it would cause build error.

Signed-off-by: Guo Dong <guo.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Maurice Ma <maurice.ma@intel.com>
Cc: Benjamin You <benjamin.you@intel.com>
Reviewed-by Sean Rhodes <sean@starlabs.systems>