b43: phy_n: Delete some useless TODO code

b43: phy_n: Delete some useless TODO code

These TODO empty code are added by
commit 19bbc5406f81 ("b43: N-PHY: partly implement SPUR workaround"). It's
been more than a decade now. I don't think anyone who wants to perfect
this workaround can follow this TODO tip exactly. Instead, it limits them
to new thinking. Remove it will be better.

No functional change.

By the way, this helps reduce some binary code size.
Before:
text    data    bss     dec     hex
74472   9967    0       84439   149d7

After:
text    data    bss     dec     hex
74408   9919    0       84327   14967

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210511034203.4122-2-thunder.leizhen@huawei.com