lmb: use a common function to check if regions overlap or are adjacent

lmb: use a common function to check if regions overlap or are adjacent

The functions to check if the two said regions are adjacent or overlap
are pretty similar in nature. Club the functionality into a single
function lmb_regions_check() and return the appropriate return value
to signify this aspect.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>