gpio: dwapb: Fix rework support for 1 interrupt per port A GPIO

Commit da069d5d ("gpio: dwapb: Rework
support for 1 interrupt per port A GPIO"), was an incremental patch that
was supposed to provide the delta between v5 and v6 patch set for
adding support for 1 interupt per port A GPIO. v5 was applied, then some
other feedback came afterwards.

However, in my haste I managed to drop the changes made to dwapb_port_property
struct. This patch includes those missing changes.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>