General forms of huge_pte_alloc, huge_pte_offset and follow_huge_pmd
are now available in mm/hugetlb.c.

This patch removes the ARM copies of these functions and activates
the general ones by enabling:
CONFIG_ARCH_WANT_GENERAL_HUGETLB
Signed-off-by: Steve Capper <steve.capper@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>