spi: spidev_test: Remove hidden temporary file when make clean

In the current code, it only removes *.o and .*.o.d file when make clean,
there still exists useless .*.o.cmd file, just remove it.

Without this patch:

[yangtiezhu@linux spi]$ make
[yangtiezhu@linux spi]$ make clean
[yangtiezhu@linux spi]$ ls -1 .*.o.cmd
.spidev_fdx-in.o.cmd
.spidev_fdx.o.cmd
.spidev_test-in.o.cmd
.spidev_test.o.cmd

With this patch:

[yangtiezhu@linux spi]$ make
[yangtiezhu@linux spi]$ make clean
[yangtiezhu@linux spi]$ ls -1 .*.o.cmd
ls: cannot access .*.o.cmd: No such file or directory

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/r/1586230512-5507-1-git-send-email-yangtiezhu@loongson.cn


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