target-*: Drop cpu_gen_code define

This symbol no longer exists.

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

target-microblaze/cpu.h

@@ -295,7 +295,6 @@ int cpu_mb_signal_handler(int host_signum, void *pinfo,
 #define cpu_init(cpu_model) CPU(cpu_mb_init(cpu_model))
 
 #define cpu_exec cpu_mb_exec
-#define cpu_gen_code cpu_mb_gen_code
 #define cpu_signal_handler cpu_mb_signal_handler
 
 /* MMU modes definitions */