Added new boundary tests & fixed boundary check bug in hwloop & mac

Created by: jessicamills

        Also: 1) clean up a couple of inaccurate comments in two earlier HW Loop
        tests; and 2) change an existing MAC test to use a non-boundary value.

gas/ChangeLog.COREV:

        * config/tc-riscv.c: Fixed bug in hardware loop operand
        boundary checks (b1 and b2).

gas/testsuite/ChangeLog.COREV:

        * cv-hwloop-16.d: Added new boundary test.
        * cv-hwloop-16.l: Likewise.
        * cv-hwloop-16.s: Likewise.
        * cv-hwloop-17.d: Likewise.
        * cv-hwloop-17.l: Likewise.
        * cv-hwloop-17.s: Likewise.
        * cv-hwloop-18.d: Likewise.
        * cv-hwloop-18.l: Likewise.
        * cv-hwloop-18.s: Likewise.
        * cv-hwloop-19.d: Likewise.
        * cv-hwloop-19.l: Likewise.
        * cv-hwloop-19.s: Likewise.
        * cv-hwloop-20.d: Likewise.
        * cv-hwloop-20.l: Likewise.
        * cv-hwloop-20.s: Likewise.
        * cv-hwloop-21.d: Likewise.
        * cv-hwloop-21.l: Likewise.
        * cv-hwloop-21.s: Likewise.
        * cv-hwloop-22.d: Likewise.
        * cv-hwloop-22.l: Likewise.
        * cv-hwloop-22.s: Likewise.
        * cv-hwloop-23.d: Likewise.
        * cv-hwloop-23.l: Likewise.
        * cv-hwloop-23.s: Likewise.
        * cv-hwloop-09.s: Fixed incorrect comment.
        * cv-hwloop-10.s: Likewise.
        * cv-mac-07.d: Added new boundary test.
        * cv-mac-07.l: Likewise.
        * cv-mac-07.s: Likewise.
        * cv-mac-08.d: Likewise.
        * cv-mac-08.l: Likewise.
        * cv-mac-08.s: Likewise.
        * cv-mac-05.l: Changed to non-boundary value.
        * cv-mac-05.s: Likewise.

Signed-off-by: Jessica Mills <jessica.mills@embecosm.com>