samples: chre: Fix format strings for size_t types

The correct printf format specifier for size_t is %zu. Without this
change the sample generates warnings like this:

warning: format '%u' expects argument of type 'unsigned int', but
argument 2 has type 'size_t' {aka 'long unsigned int'} [-Wformat=]

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
1 file changed