lib: utils: fdt_fixup: Fix compile error

When building with GCC-10 or older versions, it throws the following
error:

 CC-DEP    platform/generic/lib/utils/fdt/fdt_fixup.dep
 CC        platform/generic/lib/utils/fdt/fdt_fixup.o
lib/utils/fdt/fdt_fixup.c: In function 'fdt_reserved_memory_fixup':
lib/utils/fdt/fdt_fixup.c:376:2: error: label at end of compound statement
  376 |  next_entry:
      |  ^~~~~~~~~~

Remove the goto statement.

Resolves: https://github.com/riscv-software-src/opensbi/issues/288



Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Bin Meng <bmeng@tinylab.org>