spidev: fix double "of of" in comment

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/spi/spidev.c

@@ -42,7 +42,7 @@
  * This supports acccess to SPI devices using normal userspace I/O calls.
  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  * and often mask message boundaries, full SPI support requires full duplex
- * transfers.  There are several kinds of of internal message boundaries to
+ * transfers.  There are several kinds of internal message boundaries to
  * handle chipselect management and other protocol options.
  *
  * SPI has a character major number assigned.  We allocate minor numbers