efi_loader: Add basic EFI_TCG2_PROTOCOL support

efi_loader: Add basic EFI_TCG2_PROTOCOL support

Since U-boot EFI implementation is getting richer it makes sense to
add support for EFI_TCG2_PROTOCOL taking advantage of any hardware TPM
available on the device.

This is the initial implementation of the protocol which only adds
support for GetCapability(). It's limited in the newer and safer
TPMv2 devices.

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