microblaze: delete wrong comment about machine_early_init

machine_early_init is defined in arch/microblaze/kernel/setup.c
I do not see mach-* directory for MicroBlaze.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>

arch/microblaze/kernel/head.S

@@ -341,11 +341,6 @@ start_here:
 	/* Initialize r31 with current task address */
 	addik	r31, r0, init_task
 
-	/*
-	 * Call platform dependent initialize function.
-	 * Please see $(ARCH)/mach-$(SUBARCH)/setup.c for
-	 * the function.
-	 */
 	addik	r11, r0, machine_early_init
 	brald	r15, r11
 	nop