sh, crash: wrap crash dumping code into crash related ifdefs

Now crash codes under kernel/ folder has been split out from kexec
code, crash dumping can be separated from kexec reboot in config
items on SuperH with some adjustments.

Wrap up crash dumping codes with CONFIG_CRASH_DUMP ifdeffery, and use
IS_ENABLED(CONFIG_CRASH_RESERVE) check to decide if compiling in the
crashkernel reservation code.

Link: https://lkml.kernel.org/r/20240124051254.67105-11-bhe@redhat.com


Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Michael Kelley <mhklinux@outlook.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>