m102: set_ensm_mode in stress-test script

The fdd-4msps-t2r2 script now leaves the AD9361s in sleep mode after configuring them, so
call set_ensm_mode directly to start/stop them during the stress test.
m101: fix build with debugging enabled

Initialize 's' variable passed to strtok_r() as saveptr to quash spurious compiler
warnings which break the build when debugging is enabled.
m103: Make "clean" in Petalinux tree

Fixes the previous workaround which did a "mrproper" in Petalinux when making "clean" in
the top-level.  The top-level "reset" target can still be used to reset the Petalinux
config with a "mrproper" followed by a _defconfig for the selected SDRDC BSP.