mac80211: check return value of rhashtable_init

When rhashtable_init() fails, it returns -EINVAL.
However, since error return value of rhashtable_init is not checked,
it can cause use of uninitialized pointers.
So, fix unhandled errors of rhashtable_init.

Signed-off-by: MichelleJin <shjy180909@gmail.com>
Link: https://lore.kernel.org/r/20210927033457.1020967-4-shjy180909@gmail.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>