ARC: forbid FIRQ or multiple register banks w/ 1 IRQ priority level

Don't allow to enable multiple register banks / fast
interrupts if we have only one interrupt priority level.

NOTE: we duplicate some checks by adding dependencies to ARC
Kconfig and adding build-time checks in C code. We do it
intentionally as for some reason we can violate dependencies
in architecture-level Kconfig by adding incorrect default in
SoC-level Kconfig. Such violation happens without any
warnings / errors from the Kconfig.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>