of: Make explicit cpu_to_be32 conversion to mute sparse warning

of: Make explicit cpu_to_be32 conversion to mute sparse warning

Kernel test robot reports sparse warning:
sparse warnings: (new ones prefixed by >>)
>> drivers/of/base.c:1337:73: sparse: sparse: incorrect type in initializer
   (different base types) @@  expected restricted __be32 @@  got int @@
   drivers/of/base.c:1337:73: sparse:     expected restricted __be32
   drivers/of/base.c:1337:73: sparse:     got int

Thus, Make explicit conversions to mute warning(Although BE and LE are
exactly same in binary representation for 0/~0).

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402042134.GEb3Bgwl-lkp@intel.com/
Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Link: https://lore.kernel.org/r/20240205024033.3572617-1-dawei.li@shingroup.cn
Signed-off-by: Rob Herring <robh@kernel.org>