staging: clocking-wizard: check for a valid clk_name pointer

The clk_name gets the return value from kasprintf (part of which does the
allocation of the returned buffer). So check the return pointer
before using it for clk_register_fixed_factor.

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Reviewed-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>