Change variable name so doesn't cause issues on Zephyr OS

Created by: dlktdr

There is a define of _current in zephyr. Causes the code to not compile.

Defined here..

https://github.com/zephyrproject-rtos/zephyr/blob/cd9421a45e7254de6be913debe153dbac4be1e91/include/kernel_structs.h#L186

Suggest changing the name to __ Don't know if it's your problem or theirs.