MdePkg/BaseCacheMaintenanceLib: RISC-V: Fix InvalidateInstructionCacheRange

When the range instruction cache invalidating not supported, the whole
instruction cache should be invalidated instead.

Signed-off-by: Tuan Phan <tphan@ventanamicro.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

MdePkg/Library/BaseCacheMaintenanceLib/RiscVCache.c

@@ -76,7 +76,12 @@ InvalidateInstructionCacheRange (
   IN UINTN  Length
   )
 {
-  DEBUG ((DEBUG_ERROR, "%a:RISC-V unsupported function.\n", __FUNCTION__));
+  DEBUG (
+    (DEBUG_WARN,
+     "%a:RISC-V unsupported function.\n"
+     "Invalidating the whole instruction cache instead.\n", __func__)
+    );
+  InvalidateInstructionCache ();
   return Address;
 }