Changed the immediate order in bit maipulation instructions

Resolves the encoding problem identified in https://github.com/openhwgroup/corev-binutils-gdb/issues/68.

Files Changed:

gas/testsuite/gas/riscv:
 * cv-bitmanip-march-xcorev.d: Updated the tests with the changed
   immediate order.
cv-bitmanip-march-xcorev.s: Likewise.
cv-bitmanip-march-xcorevbitmanip.d: Likewise.
cv-bitmanip-march-xcorevbitmanip.s: Likewise.
cv-bitrev-fail.l: Likewise.
cv-bitrev-fail.s: Likewise.
cv-bitrev-pass.d: Likewise.
cv-bitrev-pass.s: Likewise.

opcodes:
 * riscv-opc.c: Changed the order of ls2 and ls3 in instructions
   cv.extract, cv.instert, cv.bclr, cv.bset, and cv.bitrev.