ARM: dts: rmobile: Drop MTD partitioning from DT

Drop the MTD partitioning from DT, since it does not describe HW
and to give way to a more flexible kernel command line partition
passing.

To retain the original partitioning, assure you have enabled
CONFIG_MTD_CMDLINE_PARTS in your kernel config and add the
following to your kernel command line:

lager:   mtdparts=spi0.0:256k(loader),4m(user),-(flash)
stout:   mtdparts=spi0.0:512k(loader),256k(uboot),256k(uboot-env),-(flash)
koelsch: mtdparts=spi0.0:512k(loader),5632k(user),-(flash)
porter:  mtdparts=spi0.0:256k(loader_prg),4m(user_prg),-(flash_fs)
wheat:   mtdparts=spi0.0:256k(loader),4m(user),-(flash)
gose:    mtdparts=spi0.0:256k(loader),4m(user),-(flash)
alt:     mtdparts=spi0.0:256k(loader),256k(system),-(user)
silk:    mtdparts=spi0.0:256k(loader),4m(user),-(flash)

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> on Koelsch
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Simon Horman <horms+renesas@verge.net.au>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-renesas-soc@vger.kernel.org
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V2: Drop the @0 anchor from the commit message, use 4m
V3: Squash the patches into one as requested by the higher ups