EmulatorPkg/RedfishPlatformCredentialLib: Check EFI_SECURE_BOOT_MODE_NAME

EmulatorPkg/RedfishPlatformCredentialLib: Check EFI_SECURE_BOOT_MODE_NAME

https://bugzilla.tianocore.org/show_bug.cgi?id=3858

Check EFI_SECURE_BOOT_MODE_NAME before setting the flags to
prohibit acquiring Redfish service credential and using Redfish
service.

Signed-off-by: Abner Chang <abner.chang@hpe.com>
Cc: Nickle Wang <nickle.wang@hpe.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Reviewed-by: Nickle Wang <nickle.wang@hpe.com>