Add driver for the RPC block in SPI-flash mode. This driver allows
access to a SPI NOR flash attached to the RPC block and does not
support RPC in Hyperflash mode. Note that this block is extremely
selective when communicating with the SPI NOR.
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
