spi: spi-gpio: fix SPI_CS_HIGH capability

[ Upstream commit b89fefda7d4e3a649129584d855be233c7465264 ]

spi-gpio is capable of dealing with active-high chip-selects.
Unfortunately, commit 4b859db2 ("spi: spi-gpio: add SPI_3WIRE
support") broke this by setting master->mode_bits, which overrides
the setting in the spi-bitbang code.  Fix this.

[Fixed a trivial conflict with SPI_3WIRE_HIZ support -- broonie]

Fixes: 4b859db2 ("spi: spi-gpio: add SPI_3WIRE support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>