KVM: x86/mmu: Move transparent_hugepage_adjust() above __direct_map()

Move thp_adjust() above __direct_map() in preparation of calling
thp_adjust() from  __direct_map() and FNAME(fetch).

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>