parisc: Fix KBUILD_IMAGE for self-extracting kernel

stable inclusion
from stable-v5.10.84
commit c27a548d3f294f5e7e70689986795f654d5c103d
bugzilla: 186030 https://gitee.com/openeuler/kernel/issues/I4QV2F

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c27a548d3f294f5e7e70689986795f654d5c103d



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commit 1d7c29b7 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: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>