efi/x86: Free efi_pgd with free_pages()

Commit

  d9e9a641 ("x86/mm/pti: Allocate a separate user PGD")

changed the PGD allocation to allocate PGD_ALLOCATION_ORDER pages, so in
the error path it should be freed using free_pages() rather than
free_page().

Commit

    06ace26f ("x86/efi: Free efi_pgd with free_pages()")

fixed one instance of this, but missed another.

Move the freeing out-of-line to avoid code duplication and fix this bug.

Fixes: d9e9a641 ("x86/mm/pti: Allocate a separate user PGD")
Link: https://lore.kernel.org/r/20201110163919.1134431-1-nivedita@alum.mit.edu


Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>