KVM: x86/mmu: Bury 32-bit PSE paging helpers in paging_tmpl.h

Move a handful of one-off macros and helpers for 32-bit PSE paging into
paging_tmpl.h and hide them behind "PTTYPE == 32".  Under no circumstance
should anything but 32-bit shadow paging care about PSE paging.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220614233328.3896033-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>