arm64: zynqmp: Fix tcminit mode param

While invoking "zynqmp tcminit mode" command (which is invalid command)
on U-Boot, it just works. Check the mode param, if it is valid then
only initialize the TCM.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20230608032152.980-2-venkatesh.abbarapu@amd.com


Signed-off-by: Michal Simek <michal.simek@amd.com>