m68k/kexec: refactor for kernel/Kconfig.kexec

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Link: https://lkml.kernel.org/r/20230712161545.87870-8-eric.devolder@oracle.comSigned-off-by: Eric DeVolder <eric.devolder@oracle.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/m68k/Kconfig

@@ -89,23 +89,8 @@ config MMU_SUN3
 	bool
 	depends on MMU && !MMU_MOTOROLA && !MMU_COLDFIRE
 
-config KEXEC
-	bool "kexec system call"
-	depends on M68KCLASSIC && MMU
-	select KEXEC_CORE
-	help
-	  kexec is a system call that implements the ability to shutdown your
-	  current kernel, and to start another kernel.  It is like a reboot
-	  but it is independent of the system firmware.   And like a reboot
-	  you can start any kernel with it, not just Linux.
-
-	  The name comes from the similarity to the exec system call.
-
-	  It is an ongoing process to be certain the hardware in a machine
-	  is properly shutdown, so do not be surprised if this code does not
-	  initially work for you.  As of this writing the exact hardware
-	  interface is strongly in flux, so no good recommendation can be
-	  made.
+config ARCH_SUPPORTS_KEXEC
+	def_bool M68KCLASSIC && MMU
 
 config BOOTINFO_PROC
 	bool "Export bootinfo in procfs"