SEMIHOSTING_SYS_OPEN macro

Semihosting call numbers and functions for OpenOCD. In OpenOCD, ARM semihosting call numbers and parameters are used for RISC-V and Xtensa targets. These conventions are not compatible with Xtensa ISS and QEMU for Xtensa, which the actual Xtensa-specific semihosting call numbers and formats; these are not supported in ESP-IDF yet.