brcmfmac: only generate random p2p address when needed

P2p spec mentioned that the p2p device address should be the globally
administered address with locally administered bit set. Therefore,
follow this guideline by default.

When the primary interface is set to a locally administered address, the
locally administered bit cannot be set again. Generate a random locally
administered address for this case.

Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Chi-Hsien Lin <chi-hsien.lin@cypress.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1587970803-77700-5-git-send-email-chi-hsien.lin@cypress.com