thermal: imx_tmu: Fix the polling default

thermal: imx_tmu: Fix the polling default

When the 'polling-delay' property is not passed via devicetree,
pdata->polling_delay keeps at 0. This causes the imx_tmu driver to get
stuck inside the busy while() loop when the CPU temperature is above
the alert point.

Fix this problem by passing a one second polling interval, which provides
a proper delay to let the system to cool down and exit the while() loop
when the temperature is below the alert point.

Signed-off-by: Fabio Estevam <festevam@denx.de>