PCI: keystone: Add TI Keystone PCIe driver

The Keystone PCIe controller is based on v3.65 version of the Designware
h/w.  Main differences are:

    1. No ATU support
    2. Legacy and MSI IRQ functions are implemented in application register
       space
    3. MSI interrupts are multiplexed over 8 IRQ lines to the Host side.

All of the application register space handing code is organized into
pci-keystone-dw.c and the functions are called from pci-keystone.c to
implement PCI controller driver.  Also add necessary DT documentation and
update the MAINTAINERS file for the driver.

[bhelgaas: spelling and whitespace fixes]
Signed-off-by: Murali Karicheri <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Acked-by: Santosh Shilimkar <[email protected]>
CC: Russell King <[email protected]>
CC: Grant Likely <[email protected]>
CC: Rob Herring <[email protected]>
CC: Mohit Kumar <[email protected]>
CC: Pratyush Anand <[email protected]>
CC: Jingoo Han <[email protected]>
CC: Richard Zhu <[email protected]>
CC: Kishon Vijay Abraham I <[email protected]>
CC: Marek Vasut <[email protected]>
CC: Arnd Bergmann <[email protected]>
CC: Pawel Moll <[email protected]>
CC: Mark Rutland <[email protected]>
CC: Ian Campbell <[email protected]>
CC: Kumar Gala <[email protected]>
CC: Randy Dunlap <[email protected]>
CC: Grant Likely <[email protected]>
diff --git a/MAINTAINERS b/MAINTAINERS
index 1ff06de..d639df9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6876,6 +6876,13 @@
 S:	Maintained
 F:	drivers/pci/host/*imx6*
 
+PCI DRIVER FOR TI KEYSTONE
+M:	Murali Karicheri <[email protected]>
+L:	[email protected]
+L:	[email protected] (moderated for non-subscribers)
+S:	Maintained
+F:	drivers/pci/host/*keystone*
+
 PCI DRIVER FOR MVEBU (Marvell Armada 370 and Armada XP SOC support)
 M:	Thomas Petazzoni <[email protected]>
 M:	Jason Cooper <[email protected]>