SFDP: Fix sector map table allocation check

When passing an allocation size directly to `std::make_unique`,
`std::nothrow` is unavailable, so any failed allocation results in
an exception which we cannot catch because Mbed OS is compiled with
`-fno-exceptions`. To fix this, chain `std::make_unique` with
`new (std::nothrow)`, and the allocated `unique_ptr` retains the
`nullptr` property.

storage/blockdevice/source/SFDP.cpp

@@ -256,7 +256,7 @@ int sfdp_parse_sector_map_table(Callback<int(bd_addr_t, void *, bd_size_t)> sfdp
      * - regions in each configuration
      *  is variable -> the size of this table is variable
      */
-    auto smptbl_buff = std::make_unique<uint8_t[]>(sfdp_info.smptbl.size);
+    auto smptbl_buff = std::unique_ptr<uint8_t[]>(new (std::nothrow) uint8_t[sfdp_info.smptbl.size]);
     if (!smptbl_buff) {
         tr_error("Failed to allocate memory");
         return -1;