MAINTAINERS: Add TPM DT bindings to TPM maintainers

Bindings for a given device class generally go to the respective
subsystem maintainers. Add the TPM bindings to the TPM
maintainers entry.

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.ogr>
Link: https://lore.kernel.org/r/20240130215917.2473250-1-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>