i2c: wmt: add missing clk_disable_unprepare() on error

Add the missing clk_disable_unprepare() before return
from wmt_i2c_reset_hardware() in the error handling case.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org # 3.11+