The BSPs provide memory for the workspace initialization via
_Memory_Get(). Most BSPs provide exactly one memory area. Only two
BSPs provide more than one memory area (arm/altera-cyclone-v and
bsps/powerpc/mpc55xxevb). Only if more than one memory area is
provided, there is a need to use _Heap_Extend(). Provide two
implementations to initialize the workspace handler and let the BSP
select one of the implementations based on the number of provided memory
areas. This gets rid of a dependency on _Heap_Extend(). It also avoids
dead code sections for most BSPs.
