message: fix USB patch file
diff: @@ -4,14 +4,14 @@ Date: Mon, 12 Mar 2018 23:49:32 -0700
  Subject: [PATCH] expose correct serial number on USB
  ---
  - Firmware/Board/v3/Src/usbd_desc.c | 15 +++++++++-------
  - 1 file changed, 8 insertions(+), 7 deletions(-)
  + Firmware/Board/v3/Src/usbd_desc.c | 9 +++++++++-------
  + 1 file changed, 1 insertions(+), 8 deletions(-)
  diff --git a/Firmware/Board/v3/Src/usbd_desc.c b/Firmware/Board/v3/Src/usbd_desc.c
  index b9c7bd0..94dc49b 100644
  --- a/Firmware/Board/v3/Src/usbd_desc.c
  +++ b/Firmware/Board/v3/Src/usbd_desc.c
  -@@ -327,14 +327,15 @@ uint8_t * USBD_FS_ManufacturerStrDescriptor(USBD_SpeedTypeDef speed, uint16_t *l
  +@@ -327,14 +327,7 @@ uint8_t * USBD_FS_ManufacturerStrDescriptor(USBD_SpeedTypeDef speed, uint16_t *l
  */
  uint8_t * USBD_FS_SerialStrDescriptor(USBD_SpeedTypeDef speed, uint16_t *length)
  {
  @@ -22,15 +22,8 @@ index b9c7bd0..94dc49b 100644
  - else
  - {
  - USBD_GetString((uint8_t *)USBD_SERIALNUMBER_STRING_FS, USBD_StrDesc, length);
  -+ uint8_t str[13]; // 12 digits + null termination
  -+ uint64_t val = serial_number;
  -+ for (size_t i = 0; i < 12; ++i) {
  -+ str[i] = "0123456789ABCDEF"[(val >> (48-4)) & 0xf];
  -+ val <<= 4;
  - }
  -+ str[12] = 0;
  -+
  -+ USBD_GetString ((uint8_t *)str, USBD_StrDesc, length);
  +- }
  ++ USBD_GetString ((uint8_t *)serial_number_str, USBD_StrDesc, length);
  return USBD_StrDesc;
  }
  