bootloader: export ets_update_cpu_frequency

components/bootloader/src/main/component.mk

@@ -5,7 +5,10 @@
 # we pull in bootloader-specific linker arguments.
 #
 
-LINKER_SCRIPTS := esp32.bootloader.ld $(IDF_PATH)/components/esp32/ld/esp32.rom.ld
+LINKER_SCRIPTS := \
+	esp32.bootloader.ld \
+	$(IDF_PATH)/components/esp32/ld/esp32.rom.ld \
+	esp32.bootloader.rom.ld
 
 COMPONENT_ADD_LDFLAGS := -L $(COMPONENT_PATH) -lmain $(addprefix -T ,$(LINKER_SCRIPTS))
 

components/bootloader/src/main/esp32.bootloader.rom.ld

@@ -0,0 +1 @@
+PROVIDE ( ets_update_cpu_frequency = 0x40008550 ); /* Updates g_ticks_per_us on the current CPU only; not on the other core */