arm64: zynqmp: Add new command for TCM initialization

arm64: zynqmp: Add new command for TCM initialization

This patch adds new zynqmp command "zynqmp tcminit mode" to
initialize TCM. TCM needs to be initialized before accessing
to avoid ECC errors. This new command helps to perform
the same. It also makes tcm_init() as global and uses it for
doing the TCM initialization.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>