wifi: cfg80211: get rid of gfp in cfg80211_bss_color_notify

Since cfg80211_bss_color_notify() is now always run in non-atomic
context, get rid of gfp_t flags in the routine signature and always use
GFP_KERNEL for netlink message allocation.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/c687724e7b53556f7a2d9cbe3d11cdcf065cb687.1675255390.git.lorenzo@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>