Place cross-core interrupt into IRAM, sanity check handler address passed into esp_intr_alloc
Cross-core interrupt handler was not marked with IRAM_ATTR.
The reason why this caused an exception is probably due to some tasks running at highest priority (these are not blocked by spi_flash_disable_caches_interrupts_and_other_cpu mechanism).
This change puts the interrupt handler into IRAM and adds a sanity check into `esp_intr_alloc`.
Reported on Github: https://github.com/espressif/esp-idf/issues/211
See merge request !404
919bb747f8