mfd: tqmx86: remove set but not used variable 'i2c_ien'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/mfd/tqmx86.c: In function ‘tqmx86_probe’:
drivers/mfd/tqmx86.c:161:29: warning: variable ‘i2c_ien’
set but not used I[-Wunused-but-set-variable]

It is never used, and so can be removed.

Signed-off-by: yu kuai <yukuai3@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>