wifi: brcmfmac: support per-vendor cfg80211 callbacks and firmware events

wifi: brcmfmac: support per-vendor cfg80211 callbacks and firmware events

Adding two vendor operations that can be used to provide per-vendor
cfg80211 callbacks and per-vendor handlers for firmware events. These
two are often related to handling interactions from user-space through
nl80211. Exporting brcmf_fweh_register() for registering the per-vendor
event handler callbacks. Some other exports for get event name string
and allowing use of brcmf_dbg() in per-vendor module.

Tested-by: James Prestwood <prestwoj@gmail.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://patch.msgid.link/20250425085519.492267-2-arend.vanspriel@broadcom.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>