Documentation/spi/spidev_test.c: fix warning

Documentation/spi/spidev_test.c:83:5: warning: no previous prototype for 'unespcape' [-Wmissing-prototypes]

fix spelling too.

Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>