riscv: enable generic PCI resource mapping

Enable the PCI resource mapping on RISC-V using the generic framework.
This allows userspace applications to mmap PCI resources using
/sys/devices/pci*/*/resource* interface.
The mmap has been tested with Intel x520-DA2 NIC card on a HiFive
Unmatched board (SiFive FU740 SoC).
Signed-off-by: NStanislaw Kardach <kda@semihalf.com>
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/pci.h

@@ -18,6 +18,8 @@
 /* RISC-V shim does not initialize PCI bus */
 #define pcibios_assign_all_busses() 1
 
+#define ARCH_GENERIC_PCI_MMAP_RESOURCE 1
+
 extern int isa_dma_bridge_buggy;
 
 #ifdef CONFIG_PCI