am62x: Handle renamed OPTEE binary

This is a backport of ecc2ae84 for v2024 since we want to update optee-os in v2024 pkg/optee-os!8 (merged).

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The OPTEE binary has been renamed in the latest optee package. Update the firmware generation script to take this into account.

Signed-off-by: Martyn Welch martyn.welch@collabora.com