target/armv8: Use 'bool' data type for cache validity flag

The variable is already used as boolean value but has the wrong data
type.

Change-Id: Ia54cfbcdad00dc15e1181c05fb97fcbaa435bb21
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/9059
Tested-by: jenkins
Reviewed-by: Richard Allen <rsaxvc@gmail.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/armv8.h

@@ -151,7 +151,7 @@ struct armv8_arch_cache {
 };
 
 struct armv8_cache_common {
-	int info;
+	bool info_valid;
 	int loc;
 	uint32_t iminline;
 	uint32_t dminline;