kernel/vm_manager: Deduplicate iterator creation in MergeAdjacentVMA

Avoids needing to read the same long sequence of code in both code
paths. Also makes it slightly nicer to read and debug, as the locals
will be able to be shown in the debugger.

src/core/hle/kernel/vm_manager.cpp

@@ -757,19 +757,22 @@ void VMManager::MergeAdjacentVMA(VirtualMemoryArea& left, const VirtualMemoryAre
     // Always merge allocated memory blocks, even when they don't share the same backing block.
     if (left.type == VMAType::AllocatedMemoryBlock &&
         (left.backing_block != right.backing_block || left.offset + left.size != right.offset)) {
+        const auto right_begin = right.backing_block->begin() + right.offset;
+        const auto right_end = right_begin + right.size;
+
         // Check if we can save work.
         if (left.offset == 0 && left.size == left.backing_block->size()) {
             // Fast case: left is an entire backing block.
-            left.backing_block->insert(left.backing_block->end(),
-                                       right.backing_block->begin() + right.offset,
-                                       right.backing_block->begin() + right.offset + right.size);
+            left.backing_block->insert(left.backing_block->end(), right_begin, right_end);
         } else {
+            const auto left_begin = left.backing_block->begin() + left.offset;
+            const auto left_end = left_begin + left.size;
+
             // Slow case: make a new memory block for left and right.
             auto new_memory = std::make_shared<PhysicalMemory>();
-            new_memory->insert(new_memory->end(), left.backing_block->begin() + left.offset,
-                               left.backing_block->begin() + left.offset + left.size);
-            new_memory->insert(new_memory->end(), right.backing_block->begin() + right.offset,
-                               right.backing_block->begin() + right.offset + right.size);
+            new_memory->insert(new_memory->end(), left_begin, left_end);
+            new_memory->insert(new_memory->end(), right_begin, right_end);
+
             left.backing_block = new_memory;
             left.offset = 0;
         }