Fix typo in atmel_spi.c

Fix cut 'n paste bug in Atmel SPI driver.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Acked-by: David Brownell <david-b@pacbell.net>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>