Solution:
DMA support must be enabled to access the PCIe endpoint through AHB-lite.
The DMA (Direct Memory Access) support has an option to enable efficient data transfer when the device acts as an initiator or a master.
For more information, refer to DMA Support section in the FPGA-IPUG-02091 (for PCIex1) and FPGA-IPUG-02126 (for PCIex4) documents.