The structure actually describes kernel frames and not kernel devices.
In most of the cases a peripherals will fit into one page, but some can
need more pages. On some platform there are no kernel devices at all.
Provides the macro NUM_KERNEL_DEVICE_FRAMES as simple way to find out if
there are mapping that hides the corner cases. This eventually allows
implementing a generic handling even on RISC-V without much overhead, so
the hack for HiFive/Spike can be removed.
Signed-off-by: Axel Heider <axelheider@gmx.de>