MAINTAINERS: Add X86 MM entry

Dave, Andy and Peter are de facto overseing the mm parts of X86. Add an
explicit maintainers entry.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Ingo Molnar <mingo@kernel.org>

MAINTAINERS

@@ -15943,6 +15943,15 @@ M:	Borislav Petkov <bp@alien8.de>
 S:	Maintained
 F:	arch/x86/kernel/cpu/microcode/*
 
+X86 MM
+M:	Dave Hansen <dave.hansen@linux.intel.com>
+M:	Andy Lutomirski <luto@kernel.org>
+M:	Peter Zijlstra <peterz@infradead.org>
+L:	linux-kernel@vger.kernel.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/mm
+S:	Maintained
+F:	arch/x86/mm/
+
 X86 PLATFORM DRIVERS
 M:	Darren Hart <dvhart@infradead.org>
 M:	Andy Shevchenko <andy@infradead.org>