arm64/mm: Drop redundant ARCH_WANT_HUGE_PMD_SHARE

There is already an ARCH_WANT_HUGE_PMD_SHARE which is being selected for
applicable configurations. Hence just drop the other redundant entry.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/1614575192-21307-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Will Deacon <will@kernel.org>