Vlv2TbltDevicePkg: Find UEFI Shell using gUefiShellFileGuid

Vlv2TbltDevicePkg: Find UEFI Shell using gUefiShellFileGuid

Remove use of PCD PcdShellFile from the IntelFrameworkModulePkg
and instead use gUefiShellFileGuid to find the UEFI Shell in
an FV.

Cc: Zailiang Sun <zailiang.sun@intel.com>
Cc: Yi Qian <yi.qian@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Zailiang Sun <zailiang.sun@intel.com>
Reviewed-by: Yi Qian <yi.qian@intel.com>