gengtype: Use HOST_SIZE_T_PRINT_UNSIGNED in another spot

This patch depends on the libiberty/vprintf-support.c change.

2024-02-12  Jakub Jelinek  <jakub@redhat.com>

	* gengtype.cc (adjust_field_rtx_def): Use HOST_SIZE_T_PRINT_UNSIGNED
	and cast to fmt_size_t instead of %lu and cast to unsigned long.