staging: kpc2000: kpc_i2c: Remove unused rw_sem

In pi2c_probe, a rw_sem is initialized and stashed off in the
i2c_device private runtime state struct. This rw_sem is never used
after initialization. Remove the rw_sem and cleanup unneeded header
inclusion.

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