[ARM] pxa: correct I2CPWR clock for pxa3xx

In commit f23d4911319fd, the pwr-i2c device name changed due to the
newly introduced device table. This patch fixes the clock so the
driver's probe will succeed again.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Acked-by: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>