efi_loader: add ExitBootServices() measurement

TCG PC Client PFP spec requires to measure
"Exit Boot Services Invocation" if ExitBootServices() is invoked.
Depending upon the return code from the ExitBootServices() call,
"Exit Boot Services Returned with Success" or "Exit Boot Services
Returned with Failure" is also measured.

Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>

Swap two ifs in efi_exit_boot_services().
efi_tcg2_notify_exit_boot_services must have EFIAPI signature.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>