Documentation: PCI: Give unique labels to sections

Make subsection labels more specific to avoid sphinx warnings.

Exact warning:
 Documentation/PCI/endpoint/pci-endpoint.rst:208: WARNING: duplicate label
pci/endpoint/pci-endpoint:other apis, other instance in Documentation/PCI/endpoint/pci-endpoint.rst

Link: https://lore.kernel.org/r/20200503214926.23748-1-bryce.steven.willey@gmail.com
Signed-off-by: Bryce Willey <Bryce.Steven.Willey@gmail.com>
[lorenzo.pieralisi@arm.com: commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring <robh@kernel.org>
diff --git a/Documentation/PCI/endpoint/pci-endpoint.rst b/Documentation/PCI/endpoint/pci-endpoint.rst
index 0e2311b..7536be44 100644
--- a/Documentation/PCI/endpoint/pci-endpoint.rst
+++ b/Documentation/PCI/endpoint/pci-endpoint.rst
@@ -78,8 +78,8 @@
    Cleanup the pci_epc_mem structure allocated during pci_epc_mem_init().
 
 
-APIs for the PCI Endpoint Function Driver
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+EPC APIs for the PCI Endpoint Function Driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 This section lists the APIs that the PCI Endpoint core provides to be used
 by the PCI endpoint function driver.
@@ -117,8 +117,8 @@
    The PCI endpoint function driver should use pci_epc_mem_free_addr() to
    free the memory space allocated using pci_epc_mem_alloc_addr().
 
-Other APIs
-~~~~~~~~~~
+Other EPC APIs
+~~~~~~~~~~~~~~
 
 There are other APIs provided by the EPC library. These are used for binding
 the EPF device with EPC device. pci-ep-cfs.c can be used as reference for
@@ -160,8 +160,8 @@
 The EPF library provides APIs to be used by the function driver and the EPC
 library to provide endpoint mode functionality.
 
-APIs for the PCI Endpoint Function Driver
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+EPF APIs for the PCI Endpoint Function Driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 This section lists the APIs that the PCI Endpoint core provides to be used
 by the PCI endpoint function driver.
@@ -204,8 +204,8 @@
    The PCI endpoint controller library invokes pci_epf_linkup() when the
    EPC device has established the connection to the host.
 
-Other APIs
-~~~~~~~~~~
+Other EPF APIs
+~~~~~~~~~~~~~~
 
 There are other APIs provided by the EPF library. These are used to notify
 the function driver when the EPF device is bound to the EPC device.