vspace: Add missing RISC-V aliases

These aliases exist for other architectures
diff --git a/libsel4vspace/arch_include/riscv/vspace/arch/page.h b/libsel4vspace/arch_include/riscv/vspace/arch/page.h
index 6a2cfa5..0ad9a1c 100644
--- a/libsel4vspace/arch_include/riscv/vspace/arch/page.h
+++ b/libsel4vspace/arch_include/riscv/vspace/arch/page.h
@@ -30,6 +30,8 @@
 
 #define seL4_ARCH_Page_Map             seL4_RISCV_Page_Map
 #define seL4_ARCH_Page_Unmap           seL4_RISCV_Page_Unmap
+#define seL4_ARCH_Page_GetAddress      seL4_RISCV_Page_GetAddress
+#define seL4_ARCH_Page_GetAddress_t    seL4_RISCV_Page_GetAddress_t
 #define seL4_ARCH_PageTable_Map        seL4_RISCV_PageTable_Map
 #define seL4_ARCH_PageTable_Unmap      seL4_RISCV_PageTable_Unmap
 #define seL4_ARCH_ASIDPool_Assign      seL4_RISCV_ASIDPool_Assign