mt76x0: rename trace symbols

Rename trace symbols that conflict with mt7601u and remove some
definitions that are not used.

Patch fixes build errors like this:
ld: drivers/net/wireless/mediatek/mt76/mt76x0/trace.o:(__tracepoints+0x0): multiple definition of `__tracepoint_set_shared_key'; drivers/net/wireless/mediatek/mt7601u/trace.o:(__tracepoints+0x0): first defined here

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 7b485902 ("mt76x0: core files")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>