thermal: rcar: fix ENR register value

On R-Mobile APE6, since it has 3 thermal zones, ENR register
has enable bits in bit 19-16, bit 11-8 and bit 3-0.

However, on R-Car gen2, since it has 1 thermal zone, ENR register has
enable bits in bit 3-0. (In other words, the write value should always
be 0 for bit 31-4 of ENR register.)

So, this patch fixes the ENR register value using I/O resource sets.

Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>