[CPU] Remove dnnl desc copy from the memory size routine (openvinotoo…

…lkit#26757)

### Details:
To process offset0 for `dnnl::blocked` desc correctly in the memory size
calculation routine we have to make another copy of the memory
descriptor, which triggers additional dynamic memory allocation via
`posix_memalign` that leads to known perf and memory overheads. But the
thing is that offset0 has not been directly used by the plugin for quite
some time, thus we don't even need to process it anymore. Therefore the
copy has been removed and a sanity check added to avoid any related
unexpected behavior.

### Tickets:
 - CVS-148778

src/plugins/intel_cpu/src/dnnl_extension_utils.cpp

@@ -171,30 +171,14 @@ DnnlMemoryDescPtr DnnlExtensionUtils::makeDescriptor(const_dnnl_memory_desc_t de
     }
 }
 
-static size_t sub_byte_data_type_multiplier(dnnl::memory::data_type dataType) {
-    switch (dataType) {
-    case dnnl::memory::data_type::nf4:
-    case dnnl::memory::data_type::s4:
-    case dnnl::memory::data_type::u4:
-    case dnnl::memory::data_type::f4_e2m1:
-        return 2;
-    default:
-        return 1;
-    }
-}
-
 size_t DnnlExtensionUtils::getMemSizeForDnnlDesc(const dnnl::memory::desc& desc) {
-    auto tmpDesc = desc;
-
-    const auto offset0 = tmpDesc.get()->offset0;
-    tmpDesc.get()->offset0 = 0;
+    OPENVINO_ASSERT(IMPLICATION(desc.get_format_kind() == dnnl::memory::format_kind::blocked, desc.get()->offset0 == 0),
+                    "Unexpected non zero offset for a dnnl blocked memory desc");
 
-    size_t size = tmpDesc.get_size();
+    size_t size = desc.get_size();
     if (size == DNNL_RUNTIME_SIZE_VAL)
         return MemoryDesc::UNDEFINED_SIZE;
 
-    size += div_up(offset0 * sizeOfDataType(tmpDesc.get_data_type()),
-                   sub_byte_data_type_multiplier(tmpDesc.get_data_type()));
     return size;
 }