gpio: tc3589x: get rid of static IRQ base

The static IRQ base is not used on any platforms with this chip
(only Ux500). Get rid of it forever, and rely on dynamic IRQ
descriptor allocation.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>