wlcore: fix usage of platform_device_add_data()

Coverity CID 986698 reports leakage of struct wlcore_platdev_data in the
probe functions of both the SPI/SDIO interfaces. The structure passed to
platform_device_add_data() is dynamically allocated and only freed in the
error paths, however, platform_device_add_data() adds a copy of the platform
specific data to the device. Move the temporary struct that is kmemdup'ed
to the stack. This issue exists since afb43e6d (wlcore: remove if_ops from
platform_data).

Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: John W. Linville <linville@tuxdriver.com>