lmb: remove overlapping region with next range

In case of new memory range to be added is coalesced
with any already added non last lmb region.

And there is possibility that, then region in which new memory
range added is not adjacent to next region. But have some
sections are overlapping.

So along with adjacency check with next lmb region,
check for overlap should be done.

In case overlap  is found, adjust and merge these two lmb
region into one.

Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Udit Kumar <u-kumar1@ti.com>