microblaze: Remove unused NO_MMU Kconfig parameter

This removes the NO_MMU Kconfig parameter,
which was no longer used anywhere in the source code
and Makefiles.

This also updates a comment refering to this parameter.
Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/Kconfig

@@ -82,11 +82,6 @@ config MMU
 	bool "MMU support"
 	default n
 
-config NO_MMU
-	bool
-	depends on !MMU
-	default y
-
 comment "Boot options"
 
 config CMDLINE_BOOL

arch/microblaze/kernel/hw_exception_handler.S

@@ -193,8 +193,8 @@
  *      -                            W   S   REG   EXC
  *
  *
- * STACK FRAME STRUCTURE (for NO_MMU)
- * ---------------------------------
+ * STACK FRAME STRUCTURE (for CONFIG_MMU=n)
+ * ----------------------------------------
  *
  *      +-------------+         + 0
  *      |     MSR     |