Add slave mode support to the MSIOF driver, in both PIO and DMA mode.

For now this only supports the transmission of messages with a size
that is known in advance.
Signed-off-by: NHisashi Nakamura <hisashi.nakamura.ak@renesas.com>
Signed-off-by: NHiromitsu Yamasaki <hiromitsu.yamasaki.ym@renesas.com>
[geert: Timeout handling cleanup, spi core integration, cancellation,
	rewording]
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NMark Brown <broonie@kernel.org>