lib: utils/fdt: Constify FDT parsing functions

Distinguish between functions which modify the devicetree and those
which only extract information from it. Other than the iterators in
fdt_domain.c, this is a mechanical conversion.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

include/sbi_utils/fdt/fdt_domain.h

@@ -70,12 +70,12 @@ void fdt_domain_fixup(void *fdt);
  *
  * @return 0 on success and negative error code on failure
  */
-int fdt_domains_populate(void *fdt);
+int fdt_domains_populate(const void *fdt);
 
 #else
 
 static inline void fdt_domain_fixup(void *fdt) { }
-static inline int fdt_domains_populate(void *fdt) { return 0; }
+static inline int fdt_domains_populate(const void *fdt) { return 0; }
 
 #endif