Add maskisr command support to Xtensa NX targets allowing masking of interrupts during single stepping. Change-Id: I3835479de8015f1a2842afd1aeab24829e385031 Signed-off-by: Henrik Mau <henrik.mau@analog.com> Reviewed-on: https://review.openocd.org/c/openocd/+/8575 Reviewed-by: Ian Thompson <ianst@cadence.com> Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com> Tested-by: jenkins