[MTD] LPDDR extended physmap driver to support LPDDR flash

Physmap is a generic map driver for different platforms and flash types.
We added support of LPDDR to physmap.
All changes here are related to introduction of new pfow_base parameter.
This parameter is valid in case of LPDDR chips only.

Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Acked-by: Jared Hulbert <jaredeh@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>