wifi: rtlwifi: cleanup few rtlxxxx_set_hw_reg() routines

Since 'u8' comparison against zero is always false, drop the
corresponding branches of AMPDU_MIN_SPACE adjustment within
'rtlxxxx_set_hw_reg()' for rtl8188ee, rtl8192ce, rtl8192de,
rtl8723ae, rtl8723be, and rtl8821ae. Compile tested only.

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

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230925090452.25633-1-dmantipov@yandex.ru