nios2: use of_property_read_bool

Use of_property_read_bool instead of open-coding it as fpcu_has.
Convert the members of struct cpuinfo from u32 to bool accordingly as
they are only used as boolean anyhow.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Acked-by: Ley Foon Tan <lftan@altera.com>