MAINTAINERS: Update QUALCOMM IOMMU after Arm SMMU drivers move

Commit e86d1aa8 ("iommu/arm-smmu: Move Arm SMMU drivers into their own
subdirectory") moved drivers/iommu/qcom_iommu.c to
drivers/iommu/arm/arm-smmu/qcom_iommu.c amongst other moves, adjusted some
sections in MAINTAINERS, but missed adjusting the QUALCOMM IOMMU section.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches    F:    drivers/iommu/qcom_iommu.c

Update the file entry in MAINTAINERS to the new location.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200825053828.4166-1-lukas.bulwahn@gmail.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

MAINTAINERS

@@ -14366,7 +14366,7 @@ M:	Rob Clark <robdclark@gmail.com>
 L:	iommu@lists.linux-foundation.org
 L:	linux-arm-msm@vger.kernel.org
 S:	Maintained
-F:	drivers/iommu/qcom_iommu.c
+F:	drivers/iommu/arm/arm-smmu/qcom_iommu.c
 
 QUALCOMM IPCC MAILBOX DRIVER
 M:	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>