kernel/device_manager: Increase virtual_end of IOCache.

We insert pages from all over the underlying disk's area,
so in order to not trip asserts, the cache must be that large too.
(It's a "null" cache, so it doesn't have any commitment.)

Fixes #19373.

src/system/kernel/device_manager/IOCache.cpp

@@ -113,6 +113,7 @@ IOCache::Init(const char* name)
 		return B_ERROR;
 	}
 	fCache = area->cache;
+	fCache->virtual_end = INT64_MAX;
 
 	// allocate arrays for pages and io vecs
 	fPages = new(std::nothrow) vm_page*[fPagesPerLine];