iommu/amd: Update git-tree in MAINTAINERS

Since the kernel.org relaunch the URL for the IOMMU git tree
changed. Update MAINTAINERS file accordingly.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

MAINTAINERS

@@ -503,7 +503,7 @@ F:	arch/x86/include/asm/geode.h
 AMD IOMMU (AMD-VI)
 M:	Joerg Roedel <joerg.roedel@amd.com>
 L:	iommu@lists.linux-foundation.org
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/joro/linux-2.6-iommu.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git
 S:	Supported
 F:	drivers/iommu/amd_iommu*.[ch]
 F:	include/linux/amd-iommu.h