dt-bindings: gpmc: Correct location of generic gpmc binding

The binding bus/ti-gpmc.txt has been moved to
memory-controllers/omap-gpmc.txt. Update all references to this in
order to make reading and understanding a given binding easier.

Cc: David Woodhouse <[e-mail]>
Cc: Brian Norris <[e-mail]>
Cc:Boris Brezillon <[e-mail]>
Cc: Marek Vasut <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: Cyrille Pitchen <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Signed-off-by: Tom Rini <[e-mail]>
Signed-off-by: Boris Brezillon <[e-mail]>

Documentation/devicetree/bindings/mtd/gpmc-nand.txt

···
 
 All timing relevant properties as well as generic gpmc child properties are
 explained in a separate documents - please refer to
-Documentation/devicetree/bindings/bus/ti-gpmc.txt
+Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 For NAND specific properties such as ECC modes or bus width, please refer to
 Documentation/devicetree/bindings/mtd/nand.txt

Documentation/devicetree/bindings/mtd/gpmc-nor.txt

···
 
 All timing relevant properties as well as generic GPMC child properties are
 explained in a separate documents. Please refer to
-Documentation/devicetree/bindings/bus/ti-gpmc.txt
+Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 Required properties:
 - bank-width: 		Width of NOR flash in bytes. GPMC supports 8-bit and
···
 
 Optional properties:
 - gpmc,XXX		Additional GPMC timings and settings parameters. See
-			Documentation/devicetree/bindings/bus/ti-gpmc.txt
+			Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 Optional properties for partition table parsing:
 - #address-cells: should be set to 1

Documentation/devicetree/bindings/mtd/gpmc-onenand.txt

···
 
 All timing relevant properties as well as generic gpmc child properties are
 explained in a separate documents - please refer to
-Documentation/devicetree/bindings/bus/ti-gpmc.txt
+Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 Required properties:
 

Documentation/devicetree/bindings/net/gpmc-eth.txt

···
 
 All timing relevant properties as well as generic GPMC child properties are
 explained in a separate documents. Please refer to
-Documentation/devicetree/bindings/bus/ti-gpmc.txt
+Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 For the properties relevant to the ethernet controller connected to the GPMC
 refer to the binding documentation of the device. For example, the documentation
···
 
 Optional properties:
 - gpmc,XXX		Additional GPMC timings and settings parameters. See
-			Documentation/devicetree/bindings/bus/ti-gpmc.txt
+			Documentation/devicetree/bindings/memory-controllers/omap-gpmc.txt
 
 Example: