KVM: SVM: Fix build error due to missing release_pages() include

KVM: SVM: Fix build error due to missing release_pages() include

Fix:

  arch/x86/kvm/svm/sev.c: In function ‘sev_pin_memory’:
  arch/x86/kvm/svm/sev.c:360:3: error: implicit declaration of function ‘release_pages’;\
	  did you mean ‘reclaim_pages’? [-Werror=implicit-function-declaration]
    360 |   release_pages(pages, npinned);
        |   ^~~~~~~~~~~~~
        |   reclaim_pages

because svm.c includes pagemap.h but the carved out sev.c needs it too.
Triggered by a randconfig build.

Fixes: eaf78265a4ab ("KVM: SVM: Move SEV code to separate file")
Signed-off-by: Borislav Petkov <bp@suse.de>
Message-Id: <20200411160927.27954-1-bp@alien8.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>