Name change for post inc operands

Issue [#60](https://github.com/openhwgroup/corev-gcc/issues/60

)

Files Changed:

  * config/riscv/riscv.cc: Name change for post inc
    operands.
  * testsuite/gcc.target/riscv/cv-mem-lb-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lb-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lbu-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lbu-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lh-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lh-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lhu-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lhu-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lw-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-lw-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sb-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sb-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sh-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sh-compile-2.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sw-compile-1.c: Likewise.
  * testsuite/gcc.target/riscv/cv-mem-sw-compile-2.c: Likewise.

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