target: consolidate existing target/algo common_magic

Unify common_magic type to unsigned int
Move common_magic to be the first member of the struct
Add unsigned specifier to xxx_COMMON_MAGIC #defines

Change-Id: If961d33232698529514ba3720e04418baf6dc6fe
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6996
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/mips_mips64.h

@@ -17,7 +17,8 @@
 #include "helper/types.h"
 
 struct mips_mips64_common {
-	int common_magic;
+	unsigned int common_magic;
+
 	struct mips64_common mips64_common;
 };