wifi: rtw89: debug: txpwr_table considers sign

Previously, value of each field is just shown as unsigned.
Now, we start to show them with sign to make things more intuitive
during debugging.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220928084336.34981-6-pkshih@realtek.com