spi: gpio: Simplify SPI_MASTER_NO_TX check in spi_gpio_probe()

Swap branches of the if statement in order to simplify it's logical
condition being checked. No functional change intended.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Chris Healy <cphealy@gmail.com>
Cc: linux-spi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>