mt76: merge mt76x0/regs.h into mt76x02_regs.h

Add missed definitions for mt76x0 into mt76x02_regs.h. Remove
mt76x0/regs.h and fixup mt76x0 code to adjust to some diffrent
registers/fields names.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>