staging: kpc2000: kpc_spi: remove fifo_depth from kp_spi struct

The kp_spi structure contains a member 'fifo_depth'. This member is
never used. Therefore, it should be removed.

Signed-off-by: Geordan Neukum <gneukum1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>