wifi: wfx: Fix error handling in wfx_core_init()

The wfx_core_init() returns without checking the retval from
sdio_register_driver().
If the sdio_register_driver() failed, the module failed to install,
leaving the wfx_spi_driver not unregistered.

Fixes: a7a91ca5 ("staging: wfx: add infrastructure for new driver")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20241022090453.84679-1-yuancan@huawei.com