HID: intel-ish-hid: Set ISH driver depends on x86

During ISH DMA enabling, some platforms (such as EHL) don't
support cache snooping, driver needs involve clflush_cache_range
API which isn't supported by all archs (such as ARM).

Considering ISH only exists on Intel platforms, add the dependence
in Kconfig to avoid build warnings or errors on other archs.

Acked-by: Pandruvada, Srinivas <srinivas.pandruvada@intel.com>
Signed-off-by: Even Xu <even.xu@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>