i2c: sprd: don't use pdev as variable name for struct device *

The pointer to a device is usually named 'dev'. These 'pdev' here look
much like copy&paste errors. Fix them to avoid confusion.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>