arm64/mm: Unify CONT_PTE_SHIFT

arm64/mm: Unify CONT_PTE_SHIFT

CONT_PTE_SHIFT actually depends on CONFIG_ARM64_CONT_SHIFT. It's
reasonable to reflect the dependency:

   * This renames CONFIG_ARM64_CONT_SHIFT to CONFIG_ARM64_CONT_PTE_SHIFT,
     so that we can introduce CONFIG_ARM64_CONT_PMD_SHIFT later.

   * CONT_{SHIFT, SIZE, MASK}, defined in page-def.h are removed as they
     are not used by anyone.

   * CONT_PTE_SHIFT is determined by CONFIG_ARM64_CONT_PTE_SHIFT.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200910095936.20307-2-gshan@redhat.com
Signed-off-by: Will Deacon <will@kernel.org>