Added usage of 'csr_next_value' function for almost all CSRs.
Created by: silabs-oysteink
All CSR instances now use MASK and RESET_VAL. Some CSRs that are dependent on other CSR next values (mnxti, mscratchcsw[l]) do not use the function. Neither does the read-only CSRs that rely on inputs not coming from other CSRs (like mimpid, mip etc).
Should fix the remaining fixes for issue #766 (closed).
SEC clean with CLIC==0 and CLIC==1.