wl12xx_sdio: enable wowlan only if enable_irq_wake() succeeded

Some platforms don't support the wake_irq, so disable wowlan
in this case, and avoid the "Unbalanced IRQ wake disable"
warning on disable_irq_wake().

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>