ARM: mm: Don't allow resizing of memblock data until "low" memory is not mapped

If allowed by call to memblock_allow_resize() - The Memblock core will
try to allocate additional memory and rearrange its internal data in
case, if there are more then INIT_MEMBLOCK_REGIONS(128) memory regions
of any type have been allocated. If this happens before Low memory is
mapped (which is done now by map_lowmem()) the system will hang, because
the Memblock core will try to operate with virtual addresses which
aren't mapped yet.

In ARM code, the memblock resizing is allowed (memblock_allow_resize())
from arm_memblock_init() which is called before map_lowmem(), so
this may lead to an error as described above.

Hence, allow Memblock resizing later during init, from bootmem_init()
when all appropriate mappings are ready.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>