nano_work: Fix never yielding from fiber
nano_work: Fix never yielding from fiber

If the delayed work FIFO never goes empty (e.g. because the work
callback keeps resubmitting or there's a very active ISR feeding items
there) then the fiber would never yield, causing all sorts of problems
for the system. Adding an explicit fiber_yield() call at the end of
the while-loop solves the issue.

Change-Id: I233b9fc18fc9db9172daf8689bd22d09952089cb
Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

explora26/zephyr,galak/zephyr,mirzak/zephyr-os,punitvara/zephyr,kraj/zephyr,tidyjiang8/zephyr-doc,ldts/zephyr,punitvara/zephyr,kraj/zephyr,nashif/zephyr,aceofall/zephyr-iotos,punitvara/zephyr,GiulianoFranchetto/zephyr,runchip/zephyr-cc3220,Vudentz/zephyr,aceofall/zephyr-iotos,finikorg/zephyr,ldts/zephyr,bboozzoo/zephyr,fbsder/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,bboozzoo/zephyr,kraj/zephyr,mbolivar/zephyr,galak/zephyr,kraj/zephyr,erwango/zephyr,fractalclone/zephyr-riscv,ldts/zephyr,Vudentz/zephyr,runchip/zephyr-cc3220,runchip/zephyr-cc3200,bigdinotech/zephyr,bboozzoo/zephyr,sharronliu/zephyr,runchip/zephyr-cc3200,finikorg/zephyr,aceofall/zephyr-iotos,zephyriot/zephyr,rsalveti/zephyr,mirzak/zephyr-os,GiulianoFranchetto/zephyr,pklazy/zephyr,mbolivar/zephyr,nashif/zephyr,runchip/zephyr-cc3220,bigdinotech/zephyr,explora26/zephyr,aceofall/zephyr-iotos,explora26/zephyr,rsalveti/zephyr,Vudentz/zephyr,punitvara/zephyr,pklazy/zephyr,fbsder/zephyr,aceofall/zephyr-iotos,sharronliu/zephyr,mbolivar/zephyr,rsalveti/zephyr,zephyriot/zephyr,bboozzoo/zephyr,punitvara/zephyr,fbsder/zephyr,fractalclone/zephyr-riscv,mirzak/zephyr-os,sharronliu/zephyr,mbolivar/zephyr,runchip/zephyr-cc3200,mirzak/zephyr-os,runchip/zephyr-cc3200,holtmann/zephyr,finikorg/zephyr,tidyjiang8/zephyr-doc,ldts/zephyr,pklazy/zephyr,nashif/zephyr,kraj/zephyr,holtmann/zephyr,holtmann/zephyr,nashif/zephyr,erwango/zephyr,tidyjiang8/zephyr-doc,zephyriot/zephyr,erwango/zephyr,ldts/zephyr,zephyriot/zephyr,bboozzoo/zephyr,explora26/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,rsalveti/zephyr,Vudentz/zephyr,Vudentz/zephyr,erwango/zephyr,holtmann/zephyr,rsalveti/zephyr,erwango/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyriot/zephyr,mbolivar/zephyr,fractalclone/zephyr-riscv,sharronliu/zephyr,fbsder/zephyr,bigdinotech/zephyr,runchip/zephyr-cc3200,zephyrproject-rtos/zephyr,finikorg/zephyr,runchip/zephyr-cc3220,holtmann/zephyr,GiulianoFranchetto/zephyr,tidyjiang8/zephyr-doc,tidyjiang8/zephyr-doc,zephyrproject-rtos/zephyr,bigdinotech/zephyr,fractalclone/zephyr-riscv,galak/zephyr,sharronliu/zephyr,runchip/zephyr-cc3220,zephyrproject-rtos/zephyr,finikorg/zephyr,pklazy/zephyr,fbsder/zephyr,mirzak/zephyr-os,bigdinotech/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,fractalclone/zephyr-riscv,pklazy/zephyr