MAINTAINERS: Add myself to X86 PLATFORM DRIVERS as a co-maintainer

For last few months Darren and I are co-maintaining PDx86 subsystem.
Make this fact official by updating MAINTAINERS database.
Acked-by: NDarren Hart <dvhart@linux.intel.com>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>

MAINTAINERS

@@ -13436,6 +13436,7 @@ F:	arch/x86/
 
 X86 PLATFORM DRIVERS
 M:	Darren Hart <dvhart@infradead.org>
+M:	Andy Shevchenko <andy@infradead.org>
 L:	platform-driver-x86@vger.kernel.org
 T:	git git://git.infradead.org/users/dvhart/linux-platform-drivers-x86.git
 S:	Maintained