feat(core/bootloader): always use empty logo

Now that the empty logo also shows model name, we do not need to draw
the full logo in bootloader at all.

core/embed/bootloader/bootui.c

@@ -189,7 +189,6 @@ void ui_screen_boot_click(void) {
 
 // welcome UI
 
-void ui_screen_welcome_model(void) { screen_welcome_model(); }
 void ui_screen_welcome(void) { screen_welcome(); }
 
 uint32_t ui_screen_intro(const vendor_header *const vhdr,

core/embed/bootloader/bootui.h

@@ -39,7 +39,6 @@ void ui_screen_boot_wait(int wait_seconds);
 void ui_screen_boot_click(void);
 void ui_click(void);
 
-void ui_screen_welcome_model(void);
 void ui_screen_welcome(void);
 
 uint32_t ui_screen_intro(const vendor_header* const vhdr,

core/embed/bootloader/main.c

@@ -421,16 +421,17 @@ int bootloader_main(void) {
     stay_in_bootloader = secfalse;
     touched = false;
 
-    // show intro animation
-
     ui_set_initial_setup(true);
 
-    ui_screen_welcome_model();
+    // keep the model screen up for a while
 #ifndef USE_BACKLIGHT
     hal_delay(1500);
 #else
+    // backlight fading takes some time so the explicit delay here is shorter
     hal_delay(1000);
 #endif
+
+    // show welcome screen
     ui_screen_welcome();
 
     // erase storage