wifi: rtw89: sar: correct TX power boundary for MAC domain

TX power in MAC domain is signed 7 bits. (unit: based on txpwr_factor_mac)
The valid range should be [-64, 63].

While the original wrong bounds might not really be encountered, still make
them correct.
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/20240412115729.8316-2-pkshih@realtek.com

drivers/net/wireless/realtek/rtw89/sar.h

@@ -7,8 +7,8 @@
 
 #include "core.h"
 
-#define RTW89_SAR_TXPWR_MAC_MAX S8_MAX
-#define RTW89_SAR_TXPWR_MAC_MIN S8_MIN
+#define RTW89_SAR_TXPWR_MAC_MAX 63
+#define RTW89_SAR_TXPWR_MAC_MIN -64
 
 struct rtw89_sar_handler {
 	const char *descr_sar_source;