tests/kernel: Add qemu_x86/x86_64 to cache test and enable cache

How cache test could be ran without CONFIG_CACHE_MANAGEMENT?

Adding qemu_x86/x86_64 as cache related API in x86 has proven to be
very brittle against changes recently: no test was at least verifying
it builds properly, not to mention running it.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>