staging: wilc1000: remove unnecessary memset in sdio_init() & wilc_spi_init()

Cleanup changes to avoid unnecessary setting 'wilc->bus_data' value to
zero as the buffer was allocated using kzalloc().

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>