wilc1000: Fix memleak in wilc_bus_probe

When devm_clk_get() returns -EPROBE_DEFER, spi_priv
should be freed just like when wilc_cfg80211_init()
fails.

Fixes: 854d66df ("staging: wilc1000: look for rtc_clk clock in spi mode")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Acked-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200820055256.24333-1-dinghao.liu@zju.edu.cn