ACPI: PPTT: Consistently use unsigned int as parameter type

The fourth parameter 'level' of function 'acpi_find_cache_level()' is
a signed interger, but its caller 'acpi_find_cache_node()' passes that
parameter an unsigned interger.

Make the paramter type inconsistency go away.

Signed-off-by: Tian Tao <tiantao6@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
[ rjw: Subject/changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>