wifi: brcmsmac: avoid function pointer casts

wifi: brcmsmac: avoid function pointer casts

An old cleanup went a little too far and causes a warning with clang-16
and higher as it breaks control flow integrity (KCFI) rules:

drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy_shim.c:64:34: error: cast from 'void (*)(struct brcms_phy *)' to 'void (*)(void *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
   64 |                         brcms_init_timer(physhim->wl, (void (*)(void *))fn,
      |                                                       ^~~~~~~~~~~~~~~~~~~~

Change this one instance back to passing a void pointer so it can be
used with the timer callback interface.

Fixes: d89a4c80601d ("staging: brcm80211: removed void * from softmac phy")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240213100548.457854-1-arnd@kernel.org