$(TOOLCHAIN)/bin/xtensa-lx106-elf-objcopy --rename-section .text=.irom0.text \
--rename-section .literal=.irom0.literal filename.o
before linking the ELF. This relocates all your code to irom.
And if you add required recipe to put iram0.text and iram0.literal in iram1_0_seg you can put all code into irom by default, and functions with __attribute__((section(".iram0.text)) will got to SRAM. This is the way I do in Frankenstein firmware.