addr_overlap: Add functions for checking address range overlap

addr_overlap: Add functions for checking address range overlap

These functions are simple but nice to have in one place.  Code
is based on in_region() from arch/arm/plat-samsung/pm-check.c.
There is similar code in memblock in memblock_addrs_overlap().

BUG=chrome-os-partner:15914
TEST=Use in future CLs.

Change-Id: I4faec4fb977215e0858bec8f0c0b988edb619457
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/37467
Reviewed-by: Jon Kliegman <kliegs@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>