ARM: prepare for removal of a bunch of <mach/memory.h> files

When the CONFIG_NO_MACH_MEMORY_H symbol is selected by a particular
machine class, the machine specific memory.h include file is no longer
used and can be removed.  In that case the equivalent information can
be obtained dynamically at runtime by enabling CONFIG_ARM_PATCH_PHYS_VIRT
or by specifying the physical memory address at kernel configuration time.

If/when all instances of mach/memory.h are removed then this symbol could
be removed.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>