docs: move m68k architecture documentation under Documentation/arch/

Architecture-specific documentation is being moved into Documentation/arch/
as a way of cleaning up the top-level documentation directory and making
the docs hierarchy more closely match the source hierarchy.  Move
Documentation/m68k into arch/ and fix all in-tree references.

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/kernel-parameters.rst

@@ -131,7 +131,7 @@ parameter is applicable::
 	LOOP	Loopback device support is enabled.
 	M68k	M68k architecture is enabled.
 			These options have more detailed description inside of
-			Documentation/m68k/kernel-options.rst.
+			Documentation/arch/m68k/kernel-options.rst.
 	MDA	MDA console support is enabled.
 	MIPS	MIPS architecture is enabled.
 	MOUSE	Appropriate mouse support is enabled.

Documentation/arch/index.rst

@@ -14,7 +14,7 @@ implementation.
    ../arm64/index
    ia64/index
    ../loongarch/index
-   ../m68k/index
+   m68k/index
    ../mips/index
    nios2/index
    openrisc/index

arch/m68k/Kconfig.machine

@@ -11,7 +11,7 @@ config AMIGA
 	help
 	  This option enables support for the Amiga series of computers. If
 	  you plan to use this kernel on an Amiga, say Y here and browse the
-	  material available in <file:Documentation/m68k>; otherwise say N.
+	  material available in <file:Documentation/arch/m68k>; otherwise say N.
 
 config ATARI
 	bool "Atari support"
@@ -23,7 +23,7 @@ config ATARI
 	  This option enables support for the 68000-based Atari series of
 	  computers (including the TT, Falcon and Medusa). If you plan to use
 	  this kernel on an Atari, say Y here and browse the material
-	  available in <file:Documentation/m68k>; otherwise say N.
+	  available in <file:Documentation/arch/m68k>; otherwise say N.
 
 config ATARI_KBD_CORE
 	bool