PCI/MSI: Rename "struct msi_chip" to "struct msi_controller"

"msi_chip" isn't very descriptive, so rename it to "msi_controller".  That
tells a little more about what it does and is already used in device tree
bindings.

No functional change.

[bhelgaas: changelog, change *only* the struct name so it's reviewable]
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Git-commit: c2791b806988100cc1c047e2b0b5c5d0914aa3b6
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Puja Gupta <pujag@codeaurora.org>