include/exec: remove warning_printed from MemoryRegion

Since d197063fcf9 (memory: move unassigned_mem_ops to memory.c) this
field is unused.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250116160306.1709518-31-alex.bennee@linaro.org>

include/exec/memory.h

@@ -784,7 +784,6 @@ struct MemoryRegion {
     bool terminates;
     bool ram_device;
     bool enabled;
-    bool warning_printed; /* For reservations */
     uint8_t vga_logging_count;
     MemoryRegion *alias;
     hwaddr alias_offset;