make nRF52840 target compilable for ARM compiler

- enable fstorage in sdk config
- remove files of modules: bootloader, DFU bootloader and UICR setings

Author: nvlsianpu

targets/TARGET_NORDIC/TARGET_NRF5_SDK13/TARGET_MCU_NRF52840/sdk/sdk_config.h

@@ -2905,6 +2905,43 @@
 #define CRC32_ENABLED 1
 #endif
 
+// <e> FSTORAGE_ENABLED - fstorage - Flash storage module
+//==========================================================
+#ifndef FSTORAGE_ENABLED
+#define FSTORAGE_ENABLED 1
+#endif
+#if  FSTORAGE_ENABLED
+// <o> FS_QUEUE_SIZE - Configures the size of the internal queue. 
+// <i> Increase this if there are many users, or if it is likely that many
+// <i> operation will be queued at once without waiting for the previous operations
+// <i> to complete. In general, increase the queue size if you frequently receive
+// <i> @ref FS_ERR_QUEUE_FULL errors when calling @ref fs_store or @ref fs_erase.
+
+#ifndef FS_QUEUE_SIZE
+#define FS_QUEUE_SIZE 4
+#endif
+
+// <o> FS_OP_MAX_RETRIES - Number attempts to execute an operation if the SoftDevice fails. 
+// <i> Increase this value if events return the @ref FS_ERR_OPERATION_TIMEOUT
+// <i> error often. The SoftDevice may fail to schedule flash access due to high BLE activity.
+
+#ifndef FS_OP_MAX_RETRIES
+#define FS_OP_MAX_RETRIES 3
+#endif
+
+// <o> FS_MAX_WRITE_SIZE_WORDS - Maximum number of words to be written to flash in a single operation. 
+// <i> Tweaking this value can increase the chances of the SoftDevice being
+// <i> able to fit flash operations in between radio activity. This value is bound by the
+// <i> maximum number of words which the SoftDevice can write to flash in a single call to
+// <i> @ref sd_flash_write, which is 256 words for nRF51 ICs and 1024 words for nRF52 ICs.
+
+#ifndef FS_MAX_WRITE_SIZE_WORDS
+#define FS_MAX_WRITE_SIZE_WORDS 1024
+#endif
+
+#endif //FSTORAGE_ENABLED
+// </e>
+
 // <q> ECC_ENABLED  - ecc - Elliptic Curve Cryptography Library