PCI: designware: Fix indent code style

Fix indent code style and replace 'MSI interrupt controller' of comment
with 'MSI controller' to fix the following checkpatch issues:

  ERROR: code indent should use tabs where possible
  WARNING: please, no spaces at the start of a line
  WARNING: line over 80 characters

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>