Fix build errors

Adjust expressions to align with the new 2-entry cache_fetch design
introduced in "Adopt 2-entry direct-mapped page cache".

Author: yy214123

.smp_stamp

@@ -0,0 +1 @@
+1

riscv.c

@@ -235,9 +235,11 @@ void mmu_invalidate_range(hart_t *vm, uint32_t start_addr, uint32_t size)
     uint32_t end_vpn = (uint32_t) end_addr >> RV_PAGE_SHIFT;
 
     /* Cache invalidation for fetch cache */
-    if (vm->cache_fetch.n_pages >= start_vpn &&
-        vm->cache_fetch.n_pages <= end_vpn)
-        vm->cache_fetch.n_pages = 0xFFFFFFFF;
+    for (int i = 0; i < 2; i++) {
+        if (vm->cache_fetch[i].n_pages >= start_vpn &&
+            vm->cache_fetch[i].n_pages <= end_vpn)
+            vm->cache_fetch[i].n_pages = 0xFFFFFFFF;
+    }
 
     /* Invalidate load cache: 8 sets × 2 ways */
     for (int set = 0; set < 8; set++) {