MAINTAINERS: Add drivers/platform/olpc to drivers/platform/x86

Andy Shevchenko sent me a simple patch that's been sitting on LKML for
10 months for OLPC and asked if I'd take it via platform/drivers/x86.
OLPC appears to be unmaintained per MAINTAINERS. Add it to
platform/drivers/x86 (unless someone else really wants it!)

Signed-off-by: Darren Hart <[e-mail]>

MAINTAINERS

···
 T:	git git://git.infradead.org/users/dvhart/linux-platform-drivers-x86.git
 S:	Maintained
 F:	drivers/platform/x86/
+F:	drivers/platform/olpc/
 
 X86 MCE INFRASTRUCTURE
 M:	Tony Luck <[e-mail]>