x86/mm: Remove unused microcode.h include

No usage for anything in that header.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230812195727.600549655@linutronix.de

arch/x86/mm/init.c

@@ -20,7 +20,6 @@
 #include <asm/tlb.h>
 #include <asm/proto.h>
 #include <asm/dma.h>		/* for MAX_DMA_PFN */
-#include <asm/microcode.h>
 #include <asm/kaslr.h>
 #include <asm/hypervisor.h>
 #include <asm/cpufeature.h>