Remove remainders of HPPA backend

Remove remainders of HPPA backend

The HPPA backend has been removed by the following commit:

    802b5081233a6b643a8b135a5facaf14bafaa77d
    tcg-hppa: Remove tcg backend

But some small pieces of the HPPA backend still survived until
today. Since we also do not have support for a HPPA target in
QEMU, we can nowadays safely remove the remaining HPPA parts
(like the disassembler code, or the detection of HPPA in the
configure script).

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>