lmb: Add 2 config to define the max number of regions

Add 2 configs CONFIG_LMB_MEMORY_REGIONS and CONFIG_LMB_RESERVED_REGIONS
to change independently the max number of the regions in lmb
library.

When CONFIG_LMB_USE_MAX_REGIONS=y, move the lmb property arrays to
struct lmb and manage the array size with the element 'max' of struct
lmb_region; their are still allocated in stack.

When CONFIG_LMB_USE_MAX_REGIONS=n, keep the current location in
struct lmb_region to allow compiler optimization.

Increase CONFIG_LMB_RESERVED_REGIONS is useful to avoid lmb errors in
bootm when the number of reserved regions (not adjacent) is reached:
+ 1 region for relocated U-Boot
+ 1 region for initrd
+ 1 region for relocated linux device tree
+ reserved memory regions present in Linux device tree.

The current limit of 8 regions is reached with only 5 reserved regions
in DT.

see Linux kernel commit bf23c51f1f49 ("memblock: Move memblock arrays
to static storage in memblock.c and make their size a variable")

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>