target/microblaze: Delay gdb_register_coprocessor() to realize

target/microblaze: Delay gdb_register_coprocessor() to realize

Currently the microblaze code calls gdb_register_coprocessor() in its
initfn.  This works, but we would like to delay setting up GDB
registers until realize.  All other target architectures only call
gdb_register_coprocessor() in realize, after the call to
cpu_exec_realizefn().

Move the microblaze gdb_register_coprocessor() use, bringing it
in line with other targets.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250429132200.605611-3-peter.maydell@linaro.org