drivers: interrupt_controller: Use macros to access line_range prop values

Compiling previous code using LLVM reveals that accessing line_range
values in runtime is not clean, as the following error is generated:
"error: initializer element is not a compile-time constant"

Replace runtime method by compile time using UTIL_INC and UTIL_x2
macros.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>