ARC: [SMP] simplify IPI code
ARC: [SMP] simplify IPI code

* ipi_data is just a word, no need to keep it as struct

* find_next_bit() not needed to loop thru a 32bit word, ffs suffices

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs