c6x: kernel: setup: Remove 'const' for local variables in machine_init

c6x: kernel: setup: Remove 'const' for local variables in machine_init

early_init_dt_scan() accepts "void *", the related warning:

    CC      arch/c6x/kernel/setup.o
  arch/c6x/kernel/setup.c: In function 'machine_init':
  arch/c6x/kernel/setup.c:290:21: warning: passing argument 1 of 'early_init_dt_scan' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
    early_init_dt_scan(fdt);
                       ^
  In file included from arch/c6x/kernel/setup.c:19:0:
  include/linux/of_fdt.h:75:13: note: expected 'void *' but argument is of type 'const void *'
   extern bool early_init_dt_scan(void *params);
               ^

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Mark Salter <msalter@redhat.com>