wifi: wilc1000: unregister wiphy only if it has been registered

In the Linux kernel, the following vulnerability has been resolved:

wifi: wilc1000: unregister wiphy only if it has been registered

There is a specific error path in probe functions in wilc drivers (both
sdio and spi) which can lead to kernel panic, as this one for example
when using SPI:

Unable to handle kernel paging request at virtual address 9f000000 when read
[9f000000] *pgd=00000000
Internal error: Oops: 5 [#1] ARM
Modules linked in: wilc1000_spi(+) crc_itu_t crc7 wilc1000 cfg80211 bluetooth ecdh_generic ecc
CPU: 0 UID: 0 PID: 106 Comm: modprobe Not tainted 6.13.0-rc3+ #22
Hardware name: Atmel SAMA5
PC is at wiphy_unregister+0x244/0xc40 [cfg80211]
LR is at wiphy_unregister+0x1c0/0xc40 [cfg80211]
[...]
wiphy_unregister [cfg80211] from wilc_netdev_cleanup+0x380/0x494 [wilc1000]
wilc_netdev_cleanup [wilc1000] from wilc_bus_probe+0x360/0x834 [wilc1000_spi]
wilc_bus_probe [wilc1000_spi] from spi_probe+0x15c/0x1d4
spi_probe from really_probe+0x270/0xb2c
really_probe from __driver_probe_device+0x1dc/0x4e8
__driver_probe_device from driver_probe_device+0x5c/0x140
driver_probe_device from __driver_attach+0x220/0x540
__driver_attach from bus_for_each_dev+0x13c/0x1a8
bus_for_each_dev from bus_add_driver+0x2a0/0x6a4
bus_add_driver from driver_register+0x27c/0x51c
driver_register from do_one_initcall+0xf8/0x564
do_one_initcall from do_init_module+0x2e4/0x82c
do_init_module from load_module+0x59a0/0x70c4
load_module from init_module_from_file+0x100/0x148
init_module_from_file from sys_finit_module+0x2fc/0x924
sys_finit_module from ret_fast_syscall+0x0/0x1c

The issue can easily be reproduced, for example by not wiring correctly
a wilc device through SPI (and so, make it unresponsive to early SPI
commands). It is due to a recent change decoupling wiphy allocation from
wiphy registration, however wilc_netdev_cleanup has not been updated
accordingly, letting it possibly call wiphy unregister on a wiphy which
has never been registered.

Fix this crash by moving wiphy_unregister/wiphy_free out of
wilc_netdev_cleanup, and by adjusting error paths in both drivers