tkey: Add a command

Add a new 'tkey' command that provides an interface to interact with
Tillitis TKey security tokens. Subcommands include:

   - info: Display device information (UDI, name, version, mode)
   - load: Load and run applications on the TKey
   - pubkey: Get the public key from a signer app
   - getkey: Derive disk encryption keys with password and USS

This command enables U-Boot to use TKey devices for secure key
derivation for full-disk encryption.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/Makefile

@@ -189,6 +189,7 @@ obj-$(CONFIG_CMD_TEMPERATURE) += temperature.o
 obj-$(CONFIG_CMD_TERMINAL) += terminal.o
 obj-$(CONFIG_CMD_TIME) += time.o
 obj-$(CONFIG_CMD_TIMER) += timer.o
+obj-$(CONFIG_CMD_TKEY) += tkey.o
 obj-$(CONFIG_CMD_TRACE) += trace.o
 obj-$(CONFIG_HUSH_PARSER) += test.o
 obj-$(CONFIG_CMD_TPM) += tpm-common.o