kernel: introduce k_float_disable system call

We introduce k_float_disable() system call, to allow threads to
disable floating point context preservation. The system call is
to be used in FP Sharing Registers mode (CONFIG_FP_SHARING=y).

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
3 files changed