gpio: pl061: remove combined interrupt

Drivers should not have a dependency on NR_IRQS. Doing so may break with
SPARSE_IRQ enabled. As there are no in kernel users of the pl061 which
have multiple instances with their interrupts combined to a single parent
interrupt, remove this functionality. If this capability is needed later,
it could be supported more cleanly by just using a devicetree property.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Cc: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Grant Likely <grant.likely@secretlab.ca>