w1_therm: Free the correct variable

commit  e62a8f34fa5a8c031a8c0cec9dfe131cdebf58e3 from
https://github.com/raspberrypi/linux.git rpi-5.4.y

commit e420637b upstream.

The problem is that we change "p_args" to point to the middle of the
string so when we free it at the end of the function it's not freeing
the same pointer that we originally allocated.

Fixes: e2c94d6f

 ("w1_therm: adding alarm sysfs entry")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200520120019.GA172354@mwanda
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Meng Li <Meng.Li@windriver.com>