Addresses a kbuild warning:

  >> WARNING: vmlinux.o(.text+0x3b764): Section mismatch in reference from
              the function olpc_dt_compatible_match() to the function
              .init.text:olpc_dt_getproperty()
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: a7a9bacb (x86/platform/olpc: Use a correct version when making up a battery node)
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>