versal: drivers: clk: Fix invalid clock name queries

The clock driver makes EEMI call to get the name of invalid clk
when executing versal_get_clock_info() function. This results in
error messages.
Added check for validating clock before saving clock attribute and
calling versal_pm_clock_get_name() in versal_get_clock_info() function.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>