Optimize K64F flash-usage for SOTP internal flash config (ARMmbed#119)

Optimize the app + firmware size to use full flash-area of the
board. This is needed for mbed-client-testapp to work with
Mbed OS 5.9.1 due to flash-size creep in Mbed OS.

Author: teetak01

configs/internal_flash_sotp.json

@@ -55,8 +55,8 @@
             "update-client.application-details": "( 40*1024)",
             "application-start-address"        : "( 41*1024)",
             "max-application-size"             : "(MBED_CONF_UPDATE_CLIENT_STORAGE_ADDRESS-MBED_CONF_APP_APPLICATION_START_ADDRESS)",
-            "update-client.storage-address"    : "(436*1024)",
-            "update-client.storage-size"       : "(388*1024)",
+            "update-client.storage-address"    : "(532*1024)",
+            "update-client.storage-size"       : "(492*1024)",
             "update-client.storage-locations"  : 1,
             "update-client.storage-page"       : 8
         }