LPC55S69_NS: Sets default TDBStore size to 32kB

Previously it was 2 pages - 1kB - which isn't sufficient to store
Reserved Area and Master Record. Reserved are requires one page and Master
Record takes two pages. With 512B page size and having two areas, active and
inactive, the minimum size requirement becomes 2 areas * 3 pages = 3kB. That
isn't enough to store any keys though.

Author: Veijo Pesonen

features/storage/kvstore/conf/tdb_internal/mbed_lib.json

@@ -15,6 +15,10 @@
             "internal_size": "0x8000",
             "internal_base_address": "0x00028000"
         },
+        "LPC55S69_NS": {
+            "internal_size": "0x8000",
+            "internal_base_address": "0x00090000"
+        },
         "DISCO_H747I": {
             "internal_size": "2*FLASH_SECTOR_SIZE",
             "internal_base_address": "0x080C0000"