MAINTAINERS: Update git URL for x86 platform drivers

The repo on kernel.org is no longer available but has a replacement at
cavan.codon.org.uk.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

MAINTAINERS

@@ -10017,7 +10017,7 @@ F:	arch/x86/
 X86 PLATFORM DRIVERS
 M:	Matthew Garrett <matthew.garrett@nebula.com>
 L:	platform-driver-x86@vger.kernel.org
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mjg59/platform-drivers-x86.git
+T:	git git://cavan.codon.org.uk/platform-drivers-x86.git
 S:	Maintained
 F:	drivers/platform/x86/