update bootloader binaries and multiple clean up

Author: hathach

README.md

@@ -142,8 +142,10 @@ but enter the `MSDEnable` command.
 This core is based on [Arduino-nRF5](https://github.com/sandeepmistry/arduino-nRF5) by Sandeep Mistry,
 which in turn is based on the [Arduino SAMD Core](https://github.com/arduino/ArduinoCore-samd).
 
-The following repos are used:
+The following libraries are used:
 
 - adafruit-nrfutil is based on Nordic Semiconductor ASA's [pc-nrfutil](https://github.com/NordicSemiconductor/pc-nrfutil)
 - [tinyusb](https://github.com/hathach/tinyusb) as usb stack
-- [nrfx](https://github.com/NordicSemiconductor/nrfx) for driver
+- [nrfx](https://github.com/NordicSemiconductor/nrfx) for peripherals driver
+- [littlefs](https://github.com/ARMmbed/littlefs) for internal file system
+- [fatfs by elm-chan](http://elm-chan.org/fsw/ff/00index_e.html) for external file system

bootloader/feather_nrf52832/6.1.0r0/feather_nrf52832_bootloader_s132_6.1.0r0.hex

@@ -278,32 +278,6 @@ static inline bool is_within(uint32_t lower, uint32_t value, uint32_t upper)
   return (lower <= value) && (value <= upper);
 }
 
-static inline uint8_t log2_of(uint32_t value)
-{
-  uint8_t result = 0; // log2 of a value is its MSB's position
-  while (value >>= 1) result++;
-
-  return result;
-}
-
-// return the number of set bits in value
-static inline uint8_t cardinality_of(uint32_t value)
-{
-  // Brian Kernighan's method goes through as many iterations as there are set bits. So if we have a 32-bit word with only
-  // the high bit set, then it will only go once through the loop
-  // Published in 1988, the C Programming Language 2nd Ed. (by Brian W. Kernighan and Dennis M. Ritchie)
-  // mentions this in exercise 2-9. On April 19, 2006 Don Knuth pointed out to me that this method
-  // "was first published by Peter Wegner in CACM 3 (1960), 322. (Also discovered independently by Derrick Lehmer and
-  // published in 1964 in a book edited by Beckenbach.)"
-  uint8_t count;
-  for (count = 0; value; count++)
-  {
-    value &= value - 1; // clear the least significant bit set
-  }
-
-  return count;
-}
-
 #ifdef __cplusplus
  }
 #endif