Fix test failures (arch not recognized)

Fix test failures (arch not recognized)

The following tests:
  - gdb.base/all-architectures-0.exp
  - gdb.base/all-architectures-1.exp
  - gdb.base/all-architectures-3.exp

fail with an "arch not recognized" error.

GDB cannot select architectures that are not supported by the ROCdbgapi
library. Remove unsupported architectures from the arch_info struct.

bfd/ChangeLog:

        * cpu-amdgcn.c (arch_info_struct): Remove unsupported
        architectures.

Change-Id: Ie9c72499fecdd64223184864cfe425330b582cf3