semihosting: move semihosting_result_t from riscv.h to the semihosting_common.h

semihosting: move semihosting_result_t from riscv.h to the semihosting_common.h

These enum values are useful for the arch level semihosting call handlers.
Currently riscv uses them, we also need similar return codes for the xtensa.

Signed-off-by: Erhan Kurubas <erhan.kurubas@espressif.com>
Change-Id: I8f63749cc203c59b07862f33edf3c393cd7e33a9
Reviewed-on: https://review.openocd.org/c/openocd/+/7039
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>