arch: arm: Fix compile error on ARMv6-M SoCs with TICKLESS_KERNEL
arch: arm: Fix compile error on ARMv6-M SoCs with TICKLESS_KERNEL

pop {lr} instruction is not supported in ARMv6-M, fixed by
using pop {r0}; mov lr, r0; instructions.

Jira: ZEP-2222

Signed-off-by: Vinayak Kariappa Chettimada <e780c9f87dc729ad454f47292ad82c8652353064@nordicsemi.no>

bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr,bigdinotech/zephyr