staging: wilc1000: use flexible-array member instead of zero-length array

staging: wilc1000: use flexible-array member instead of zero-length array

Use flexible-array member introduced in C99 instead of zero-length
array. Most of zero-length array was already taken care in previous
patch [1]. Now modified few more cases which were not handled earlier.

[1]. https://patchwork.kernel.org/patch/11394197/

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200302162226.4196-4-ajay.kathat@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>