mfd: qcom-pm8xxx: Remove set but unused variable 'rev'

Variable rev is not effectively used in the function, so delete it.

  drivers/mfd/qcom-pm8xxx.c:513:6: warning: variable 'rev' set but not used.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=3558


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221227081921.56448-1-jiapeng.chong@linux.alibaba.com