On NUC472, on wake-up from power-down mode, we may meet hard fault or some other
unknown error. Before its cause is found, we enter idle mode instead for a workaround.
To simulate power-down mode with idle mode, we also disable us_ticker during
power-down period.
Add sleep/deepsleep functions to platform layer which are replacing HAL
functions with the same name, rename existing symbols in HAL layer
to hal_sleep/hal_deepsleep. This way sleep functions
are always available, even if target doesn't implement them, which makes
the code using sleep clearer. It also enables us to make decision on in
which builds (debug/release) the sleep will be enabled.
ccli8
Sam Grove
Bartek Szatkowski
Christopher Haster