pinctrl: ti: The IODelay driver is a DRA7xxx feature so depend on that SoC

As the IODelay driver is a hardware feature of the  DRA7xxx SoC
depend on that SoC and compile test.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>