soc/rtc_clk: reduce data size by disabling CSWTCH generation

Saves about 200 bytes of DRAM at the expense of 4 bytes in IRAM.

components/soc/component.mk

@@ -4,3 +4,5 @@ SOC_NAME := esp32
 COMPONENT_SRCDIRS := $(SOC_NAME) src/
 
 COMPONENT_ADD_INCLUDEDIRS := $(SOC_NAME)/include include
+
+-include $(COMPONENT_PATH)/$(SOC_NAME)/component.mk

components/soc/esp32/component.mk

@@ -0,0 +1 @@
+esp32/rtc_clk.o: CFLAGS += -fno-jump-tables -fno-tree-switch-conversion