MLK-22035-1 lmb: Add lmb_reserve_overlap for fdt reserved memory

MLK-22035-1 lmb: Add lmb_reserve_overlap for fdt reserved memory

Previous patch "MLK-21885 lmb: Handle the overlap case for lmb reserve" adds
the overlap support to lmb reserve. However, u-boot has some places to use the
lmb_reserve when allocating memory in loading images.  If we allowed overlap
in this function, it means images loading address can overlap each other and
cause the address check mechanism not work.

So add another function to allow overlap and only use it for fdt reserved-memory
nodes. The FDT reserved-memory is ok to merge with other reserved memory, since
this won't break image loading address check.

Signed-off-by: Ye Li <ye.li@nxp.com>