parisc: Fix KBUILD_IMAGE for self-extracting kernel

parisc: Fix KBUILD_IMAGE for self-extracting kernel

BugLink: https://bugs.launchpad.net/bugs/1956791
commit 1d7c29b77725d05faff6754d2f5e7c147aedcf93 upstream.

Default KBUILD_IMAGE to $(boot)/bzImage if a self-extracting
(CONFIG_PARISC_SELF_EXTRACT=y) kernel is to be built.
This fixes the bindeb-pkg make target.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>