KVM: ARM: Cleanup KVM 32-bit huge page patch

The huge pages patch was using an ugly cast and we keep forgetting why
the VM_BUG_ON is relevant in stage2_set_pte, add a comment.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
KVM: ARM: Depend on HUGETLB_PAGE in defconfig

The pmd_huge predicat returns 0, even for huge pmd's, when the
HUGETLB_PAGE config option is not selected.  Until we have a proper fix,
make sure the THP support code in KVM/ARM works.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
KVM: ARM: Don't bard on SWIs in the host

This is a hack so we can measure VMEXIT performance.

DO NOT MERGE UPSTREAM.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>