cmd: Add support for optee commands

Add the basic 'hello world ta' command which increment
of the value passed. This provides easy test for
establishing a session with OP-TEE TA and verify.

It includes following "hello world ta" subcommands:
optee hello; default value '0' is passed and gets incremented.
optee hello <value>; value to increment via OP-TEE HELLO
WORLD TA.

To enable the OP-TEE side HELLO WORLD example please refer
https://optee.readthedocs.io/en/latest/building/gits/optee_examples/optee_examples.html

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
(cherry picked from commit e3cf80fbe0)

cmd/Makefile

@@ -126,6 +126,7 @@ obj-$(CONFIG_CMD_PAUSE) += pause.o
 obj-$(CONFIG_CMD_SLEEP) += sleep.o
 obj-$(CONFIG_CMD_MMC) += mmc.o
 obj-$(CONFIG_CMD_OPTEE_RPMB) += optee_rpmb.o
+obj-$(CONFIG_CMD_OPTEE) += optee.o
 obj-$(CONFIG_CMD_MP) += mp.o
 obj-$(CONFIG_CMD_MTD) += mtd.o
 obj-$(CONFIG_CMD_MTDPARTS) += mtdparts.o