efi_loader: add missing parameter check for EFI_TCG2_PROTOCOL api

TCG EFI Protocol Specification defines the required parameter
checking and return value for each API.
This commit adds the missing parameter check and
fixes the wrong return value to comply the specification.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>