Merge branch 'bugfix/crosscore_int_iram' into 'master'

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