wifi: rtlwifi: cleanup few rtlxxx_tx_fill_desc() routines

Remove unreachable branches in 'rtl92ce_tx_fill_desc()',
'rtl92cu_tx_fill_desc()' and 'rtl8723e_tx_fill_desc()'.
Compile tested only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240109104735.140550-1-dmantipov@yandex.ru