Consolidate code related to setting up physical memory configuration into
a new physmem.c file.  The new code provides helper routines that can be
used by legacy SoCs and newer FDT-based systems.  There are routines to
add one or more regions of physically contiguous ram, and exclude one or
more physically contiguous regions of ram.  Ram can be excluded from crash
dumps, from being given over to the vm system for allocation management,
or both.  After all the included and excluded regions have been added,
arm_physmem_init_kernel_globals() processes the regions into the global
dump_avail and phys_avail arrays and realmem and physmem variables that
communicate memory configuration to the rest of the kernel.

Convert all existing SoCs to use the new helper code.