rtw88: add dump fw crash log

This patch adds a function which is able to dump firmware fifo when
firmware crashes. If firmware needs more than one time to dump all logs,
it will set a bit called "more bit" in the header of the first log, and
driver needs to set a register to inform firmware that it is ready for the
next dump.

Signed-off-by: Tzu-En Huang <tehuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200925061219.23754-5-tehuang@realtek.com