Move the CONFIG_MCHECK_HEAP_PROTECTION block after the standard
includes so that size_t and string functions are available for
the inline MALLOC_ZERO and MALLOC_COPY functions.
Add the <string.h> and <linux/types.h> includes needed for mcheck.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>