soc: xilinx: vcu: Update vcu init/reset sequence

soc: xilinx: vcu: Update vcu init/reset sequence

Updated vcu init/reset sequence as per design changes.
If VCU reset GPIO is available then do assert and de-assert it before
enabling/disabling gasket isolation.
This GPIO is added because gasket isolation will be removed during startup
that requires access to SLCR register space. Post startup, the ownership of
the register interface lies with logiCORE IP

Signed-off-by: Dhaval Shah <dhaval.shah@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>