spi: spidev_test: Check input_tx and input_file first after parse options

It is better to check input_tx and input_file first after parse options.
Otherwise, it will do some useless operations when both -p and --input
are selected.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/1581567368-8055-2-git-send-email-yangtiezhu@loongson.cn


Signed-off-by: Mark Brown <broonie@kernel.org>