spi: rspi: Fix sequencer reset during initialization

[ Upstream commit 26843bb128590edd7eba1ad7ce22e4b9f1066ce3 ]

While the sequencer is reset after each SPI message since commit
880c6d11 ("spi: rspi: Add support for Quad and Dual SPI
Transfers on QSPI"), it was never reset for the first message, thus
relying on reset state or bootloader settings.

Fix this by initializing it explicitly during configuration.

Fixes: 0b2182dd ("spi: add support for Renesas RSPI")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>