libc.h:Fixed the problem of multiple define appearing in arch_xxx.S after opening kasan

The reason is that libc.h needs to check whether CONFIG is enabled before the corresponding macro is enabled

Error scene:
arm-none-eabi-ld: /home/crafcat7/SSD/xxx/xxx-dev/nuttx/staging/libc.a(arch_libc.o): in function `memmove':
/home/crafcat7/SSD/xxx/xxx-dev/nuttx/libs/libc/machine/arch_libc.c:146: multiple definition of `memmove'; /home/crafcat7/SSD/xxx/xxx-dev/nuttx/staging/libc.a(arch_memmove.o):/home/crafcat7/SSD/xxx/xxx-dev/nuttx/libs/libc/machine/arm/armv8-m/gnu/arch_memmove.S:56: first defined here

Signed-off-by: chenrun1 <chenrun1@xiaomi.com>

libs/libc/libc.h

@@ -25,6 +25,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <nuttx/config.h>
+
 #ifndef __ASSEMBLY__
 #  include <sys/types.h>
 #  include <stdbool.h>