mm: arm: Fix BUG() while do iova range checking

This BUG() is triggered when addr + size(like 0x80000000 + 0x80000000)
overflows to 0. It is the implementation only on ARM32.
Hence fix it by decreasing 1 on both sides.
By the way, adding the checking of overflow addr + size to avoid BUG()
in this case.

Change-Id: I1955fa69cd494bdde24f9dbe32879973d65d6fe0
Signed-off-by: Zhenhua Huang <zhenhuah@codeaurora.org>