Changed post increment load/store encodings to CV32E40P

 gas/testsuite/gas/riscv:
  * cv-mem-lbrr.d: Updated expected output of test.
  * cv-mem-lbrrpost.d: Likewise.
  * cv-mem-lburr.d: Likewise.
  * cv-mem-lburrpost.d: Likewise.
  * cv-mem-lhrr.d: Likewise.
  * cv-mem-lhrrpost.d: Likewise.
  * cv-mem-lhurr.d: Likewise.
  * cv-mem-lhurrpost.d: Likewise.
  * cv-mem-lwrr.d: Likewise.
  * cv-mem-lwrrpost.d: Likewise.
  * cv-mem-march-rv32i-xcorev.d: Likewise.
  * cv-mem-sbrr.d: Likewise.
  * cv-mem-sbrrpost.d: Likewise.
  * cv-mem-shrr.d: Likewise.
  * cv-mem-shrrpost.d: Likewise.
  * cv-mem-swrr.d: Likewise.
  * cv-mem-swrrpost.d: Likewise.

 include/opcode:
  * riscv-opc.h: Changed post increment load/store encodings to
    CV32E40P.

Signed-off-by: Mary Bennett <mary.bennett@embecosm.com>