rtw88/rtw89: avoid duplicate top-level directory with debugfs

If people like me having multiple cards in the same system
creating the debugfs dirctory leads to a panic upon attaching
the 2nd card due to the duplicate name.
Rather than using the hard coded driver name, use the device name
(e.g., rtw880, rtw881, rtw882).
This solves two issues: it avoids the duplicate name and we get
individual debugging/statistic information for each card.

Sponsored by: The FreeBSD Foundation
X-Note: ath1[01]k and mt76 likely will need a similar change

(cherry picked from commit b4886c4ece3e692c294aa853da7aec849f8d00a2)