chore: drop the 64-bit division and keep INFO_UF2.TXT text in flash only (#74)

* fix(dfu): compute the startup timeout ticks in 32 bits

APP_TIMER_TICKS is 64-bit and pulls __udivmoddi4 into the image for one
call site. The 32-bit form gives the same tick count for any timeout under
131 s.

* chore: keep INFO_UF2.TXT text in flash only and build the file in bss

Author: jamesarich

lib/sdk11/components/libraries/bootloader_dfu/bootloader.c

@@ -345,7 +345,8 @@ uint32_t bootloader_dfu_start(bool ota, uint32_t timeout_ms, bool cancel_timeout
       dfu_startup_packet_received = false;
 
       app_timer_create(&_dfu_startup_timer, APP_TIMER_MODE_SINGLE_SHOT, dfu_startup_timer_handler);
-      app_timer_start(_dfu_startup_timer, APP_TIMER_TICKS(timeout_ms), NULL);
+      // APP_TIMER_TICKS is 64-bit and pulls __udivmoddi4 into the image; this is the same rounding for timeout_ms < 131 s.
+      app_timer_start(_dfu_startup_timer, ((timeout_ms * 32768u + 500u) / 1000u), NULL);
     }
 
     err_code = dfu_transport_serial_update_start();

src/usb/uf2/ghostfat.c

@@ -132,7 +132,8 @@ STATIC_ASSERT(FAT_ENTRIES_PER_SECTOR                       ==       256); // FAT
     "Date: " __DATE__ "\r\n" \
     "Factory-Erase: UF2 family 0x4D455348\r\n"
 
-char infoUf2File[128*3] = INFO_UF2_TEXT;
+static const char infoUf2Text[] = INFO_UF2_TEXT;
+char infoUf2File[128*3];
 // uf2_init() appends "SoftDevice: S140 7.3.0\r\n" at runtime; 40 covers the
 // widest values the id/version fields can print
 STATIC_ASSERT(sizeof(INFO_UF2_TEXT) + 40 <= sizeof(infoUf2File));
@@ -309,6 +310,7 @@ static inline bool in_uicr_space(uint32_t addr)
 
 void uf2_init(void)
 {
+  strcpy(infoUf2File, infoUf2Text);
   strcat(infoUf2File, "SoftDevice: ");
 
   if ( is_sd_existed() )