lib: lmb: reserving overlapping regions should fail

lib: lmb: reserving overlapping regions should fail

lmb_add_region handles overlapping regions wrong: instead of merging
or rejecting to add a new reserved region that overlaps an existing
one, it just adds the new region.

Since internally the same function is used for lmb_alloc, change
lmb_add_region to reject overlapping regions.

Also, to keep reserved memory correct after 'free', reserved entries
created by allocating memory must not set their size to a multiple
of alignment but to the original size. This ensures the reserved
region is completely removed when the caller calls 'lmb_free', as
this one takes the same size as passed to 'lmb_alloc' etc.

Add test to assert this.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>